It's a pretty straightforward design. I made the bunk bed version first since I wanted a place to put my Pebble smart watch at night without having to get off from my bunk bed. The bed version is designed for beds with holes on the corners to support the rod for a bunk bed. I then figured I might as well just take the same fit and use it to make a version that can just stand on its own.

It's designed for the original pebble. I have no idea if it will work with a pebble steel or pebble time, but anyone is obviously welcome to try either of those watches.

I also uploaded the STEP files, so feel free to make any improvements.