This is a mashup of two other models I found on Thingiverse - https://www.thingiverse.com/thing:5704716 for the Magquad lock mount, and https://www.thingiverse.com/thing:4935721 for the Galaxy fold 3 case.

I have not yet tested this design, but the it's meant for the quadlock magring to go in the open circle, so it can be compatible with magsafe and quadlock mounts.