I wanted to mount my M5Stack Atom Matrix on top of a camera. So i had a friend work something out for me. I have since refined it with a screw and nuts to fit into a hotshot without any screws or other equipment. the bigger nut locks it in place with the hotshot the smaller nut locks the holder in place.

I got inspired from this Project: https://www.thingiverse.com/thing:4793782

I print at 100% Infill for it to be stable, but 20% is enough too.