Summary

Two large pieces are best printed in PLA. Cables (including Ethernet and USB-A) can be routed inside. The top platform uses clips along with US number 6 screws and nuts to hold a thing in place (in the pictures I have one of my Raspberry Pi holders shown, not in this design but to be uploaded soon).

The bottom part is meant to be screwed or bolted down.

The holes will take screw(s) to maintain a constant height.