My jig started life as an IKEA chopping board, after some cutting, machining, and a few bits of common hardware, this is how it turned out:

The polyethylene material resists pretty much any chemicals a modeller is ever likely to throw at it. Even CA adhesive can't stick to this, which is why I had to assemble it using fasteners.
For those interested, I created a video to fully detail the construction of this jig, and demonstrate its use: https://youtu.be/BGDpVvuYbUs
Cheers!