Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4855761.
THIS IS A WIP! I am ACTIVELY working on a v2 that will have more room for the mouse while still supporting the palm. As it is, it kind of pushes longer mice away from your hand.
This is a palm rest meant to glide behind your mouse as you move it. Rest the back part of your palm on it while you use the mouse and it should keep your wrist and everything else in-line to help with carpal tunnel.
Due to the "quick and dirty" nature of this design I didn't bother laying the model flat on a surface so when slicing you'll have to lay it flat yourself. Cura has a built in feature called "Lay Flat" in the rotation menu that works perfectly for me.
Disclaimer: This was made with a 3D-Scan of MY hand so this likely won't work for everyone, however it should be good enough for most people