This is probably the simplest spool holder you'll find here. Just print it and use it, no screws needed for assembly.
I designed it to be mounted on a 2020 aluminum extrusion profile.
You just need to print it and snap it wherever you think it suits the best for your printer (as long as the profile is placed horizontally of course). If you would prefer to use screws even they are not really required, you have the holes to place two m3 screws that will fasten with 2 square nuts that would be placed within the 2020 aluminum profile.
If you make any donation to help me keep working on my designs, as a sign of appreciation, I'll send you the fusion 360 files.