To print this to spec, there are some post processing to do. These are the additional equipment you need, and what they are for.

General requirement: Your printer should have a tolerant of at worst 0.3 mm. Meaning if you print a hole size 2.05, you should be able to put a 1.75 filament through it. (2.05-1.75 = 0.3). Your test cube should come out at worst 19.9 - 20.1 mm x 19.9 - 20.1 mm x 19.9 - 20.1 mm. Anything worse than that, parts might not stick together.

I print and use this model printed with PLA.

Do not use silky filament. It will not survive the assembly process.

The Case (The simplest model to print)

1. Print with support. You need the support for the side grip that prevent the phone from falling out from the front. The grip is designed to grip the phone with silicone sock on, so it's quite pronounce from the side of the case. There is no way you can print it without drooping if you don't use support.
2. Layer resolution should be 0.2. Lower is ok. Higher and you might mess up the locking mechanism for the ring and the hinge.

The Front Cover (2 options w or w/o a clear panel): You can add engraving to it even when your printer has only 1 nozzle.

How to add engraving?

1. Find your pattern. Choose the one with Black and White. Do not choose something with lots of fine line unless you are very sure your printer can handle that kind of image resolution.

2. Choose your model editor

A: TinkerCad

2A.1 Convert the model to SVG. Using free online tool is ok.

2A.2 Import to TinkerCad

2A.3 Set the imported pattern to 0.4 (2 layers) height

2A.4 Put the image on the Front Cover model in hole mode. NOTE! Make sure you align it in the right direction. I've messed up my print too many times because I put the front side up forgetting that the cover is printed face down. This results in the engrave coming out a mirror image (switch left to right). Basically, if you watch from the front, you should see the image in the right mode but if you watch from the default printing direction it should be mirrored.

2A.5 Copy and past the pattern on the same position

2A.6 Cut the hole to the front cover

2A.7 Export the cover, and the pattern as separated models

B: Windows 10 3D Builder (free from Windows Store)

2B.1 Import your image to the app. Choose Contour mode, height 0.4

2B.2 Save the model of the image

2B.3 Import the front cover model

2B.4 Cut the hole in front cover model using Edit -> Subtract

2B.5 Export the front cover model

3. When load to your slicer, align the pattern inside the hole. There are a couple of tips that you can use but it is ok to just eyeball it.

4. Delete the model for the front panel. The pattern should remain on the position. Slice it for engraving gcode

5. Once saved, CTRL+Z to get the cover back. Then, delete the engrave model. Slice for the front cover gcode.

6. Set your print profile to do Z-hop for 0.5mm on retraction. Slice without support

7. When print, print the engrave pattern first. Use whatever color you want for it.

8. After the engrave is printed, do not remove the bed. Keep it right where it is. Home the nozzle without messing the print bed. It is recommend to check for string on the print bed. Remove the string. Make the print bed as free as possible without moving the printed model on the bed. I suggest using knife and plier to pick the string off one by one. If your image does not have too many fine lines, the string should not be too bad

9. Finally, print the front cover right after. The Z hop should keep your nozzle from hitting the printed engraving. The model is 0.4mm thick and z-hop is 0.5mm. The side of the engraving should have molten plastic laid and the heat will fuse the engraving with the front cover

I don't want engraving: Simply print the front cover. With or Without the panel window, does not matter. Resolution 0.2, no support. If printed with the case as a set, use support blocker.

Front Panel: Clear panel for Youtube VDO in portrait mode. I recommend you use the model Panel Size to measure a clear acrylic panel and cut it to size. Use acrylic. It is much easier. Simply glue the panel to the inside of the front cover. I use super glue. Let the cover to rest for a day. If you don't, glue may leave white residue on the screen of the phone.

If you don't have acrylic, but you do have hot air gun and clear PLA filament, this is how to make a clear panel

1. Print Panel Size with any resolution. This is just for a size measurement.

2. Slice the Panel Material with as small layer height as you can. I use 0.04

3. Set material flow rate to 100% or a bit above

4. Set temp to maximum temp for the PLA - 5. I set it to 220c

5. Enable ironing

6. Disable retraction

7. Print the material model with clear filament. A bit of over extrusion is expected

8. Put the model on somewhere flat and can take a lot of heat. I use concrete floor once, and granite block after that, either works just fine.

9. Wear your eye protection, in case the base mentioned in 8 shatters. Prepare your heat gun.

10. Use hot air gun to blow the PLA print. Start from a corner. Blow until it becomes molten and glossy. Don't mind if it isn't clear yet.

11. Move the hot air gun from the corner to another corner. Use the air pressure to drive the ripple away. Try not to have the material bubbled up on the underside

12. Once 2 corners are molten, move the hot air to the middle. Again, drive away ripple. Do until molten. Don't mind if it's not clear yet. You just want it to get glossy. Do so until the entire material is molten. Wait until cool.

13. Remove the material. Turn it over.

14. Repeat 10 - 12 from the other side. This time, you should see that the material become clear as it becomes glossy. Do this right and you have a serviceable clear panel.

15. Use the Panel Size model to cut the clear material. Cut with scissor. Glue the clear panel to the inside of the Front Cover like a piece of acrylic

Links: To connect the Front Cover with the Case

Simply print with the holes up. You will need 2 of each type of links, except the smallest you need 4.

Finger Ring:

1. Print with support

2. Use support blocker to prevent support inside the ring but not under the ring. You need the inside of the ring to have no support or it will not turn at all.

Assembly:

1. Once all are printed and all support removed, prepare some leftover 1.75 PLA filament and filament cutter with you. A super glue is needed too.

2. Turn your phone off. Put it inside silicone sock.

3. You can use hot air gun to soften the case but I don't use it.

4. Put your phone in. Insert from the right side (with openning). Set it until you feel a strong resistant. The phone should touch the side without openning almost entirely.

5. Slide the lower side (with the pen) in first. Then, push the top in decisively. The soft TPU sock should allow the phone to slide in and not slip out.

6. Align the links with the case, or the front cover. Use 1.75 filament as a connector. The alignment from the case to the front cover is like this:
Large - Small - Large - Space - Small
[Smallest - Largest - Largest - Smallest] - Space - [Smallest - Smallest] : The smallest 2 should encapsulate the portion they are assigned to.
The front cover will fit right into the space left by the links.

7. Super glue the smallest link to the filament connector. Without glue, these links fall off easily. Make sure you turn the front cover to the right side. The flat side is to go outside. Once super glued, you cannot remove the links without destroying it.

8. With the front panel installed, do not let the glue touches the screen. There is invisible vapor from the glue curing and it will leave white patch on the screen. I recommend you don't close the lid for 24 hours, or do so with a piece of paper to protect the screen.

9. Clear the support off the back ring and turn it around. Make sure it works.

10. Install the back ring by snapping it in. If your printer has a good enouch tolerant, this should not be an issue. If you have elephant foot, simply grind it off.

11. Once seated, insert 5 1.75 PLA filament until they come out the other side of the case. This will lock the back ring in.

12. Enjoy your new print. This is not an easy print. Well done.

Workaround in case you don't have TPU sock

If you don't have a TPU sock for the phone, you can glue the phone to the case. I don't recommend you scale the case because the 1.75mm filament cannot be inserted. I also am not going to do a model that you can press the phone in because that might scratch your phone in the process, and I'm not going to test that one my phone. To glue your phone, do this

1. Put a paper tape on the entire back side of your phone.

2. Put a paper tape on the entire inside (not to the side) of the case

3. Measure how you're going to place the phone inside the case. Take note on the camera. Try to avoid putting the rim to the case. Allow some space to allow transfer of force in case of a drop.

4. Apply super glue on the paper tape inside the case

5. Put the phone in. Let the glue cure. This will glue the tape to the tape. It is surprisingly strong, you will be amazed if you've never done it.

Whew! This is a long writing section. Hope it helps and hope you enjoy the print. If you appreciate my work, please buy me a coffee using the Tip. Thanks a lot.
If you want the engraving done for you, buy me a coffee and msg me. I can do it the STL for you.