https://imgur.com/a/b7SvB
This is a fixture I made for milling a product I'm manufacturing from 1/2" acrylic sheet. I also use it for milling circuit boards and for engraving various labels.
The fixture is made from Azek (white plastic lumber found at Home Depot). There are 1/8" pins for locating the work. The copper piece is a 1/2" coupler which I use to zero the x&y axes with a Mach3 macro. The rubber seal is 1/8" neoprene, and it sits in a 1/8" x 0.090" deep groove.
This was my first shot at this thing, and it's doing what I needed it to do.. It's easy and cheap enough to crank out specialty fixtures as I need them, with Fusion 360.