I don't know if this will even work for  anyone else, but here it  is.  Peg presses in and is fastened to corner with 2 screws.  Screw holes are chamfered for shorty drywall screws.  Pre-drill the holes in the wood.

Printed at .2 layer height

enough walls so there is no infill  3 or 4

3 top/bottom

15-20 infill