The Raspberry Pi 7" Touchscreen is an amazing, affordable piece of tech. I decided I wanted to mount one to my wall to use for home automation. But none of the DIY mounts I found online dealt with the problem of how to flush mount it with no exposed wires. This project shows you how to do it using a 3-gang electrical box and a handful of 3D-printed parts.
The full project description is here on Instructables.com: https://www.instructables.com/id/Flush-Wall-Mounted-Raspberry-Pi-Touchscreen/
After some iteration, I arrived at an improved design which makes the faceplate stiffer, and brings the bezel closer to the wall. These are faceplate_v2 and bezel_v2. I recommend using the v2 parts instead of the original ones, but left the originals here since they're the ones pictures in the Instructable.