I designed and built a couple of these to use with out 4x4 CNC router with a ATC.  This one does not have the rubber edging around the holes yet.  I used a 1/16" wall rubber channel I found at an auto glass shop.  Usually used on glass or plastic windows.  Powder Coated after assembly.
Assembled with 6-32 press in flushnuts and screws, but pop rivet or screws and nuts would work as well.

James