I designed the flip phone loosely based on the Nokia 2760.
Flips easily, doesn't lock in place but friction does the job. Print the "screen" and the "keys" part with the flat side down.The pin is slightly too thick but the right length so I recommend scaling it down (don't scale the length) I did, 90%,90% and 100%. Print it upright. Make it 100% infill to make it as strong as a real Nokia ;)