If you ever head to IKEA, be sure to pick up a few LEGITIM cutting boards. They cost $1.99 each—though sometimes less—and are great for putting together a jig or if you ever just need a little HDPE for a project. They're 34 cm x 24 cm x 8 mm, with rounded corners and a single cutout on one end for gripping or hanging, and textured on both sides.
If you've never worked with HDPE, it's a joy. It's easy to work with hand tools, won't crack when you drill or screw into it, machines like butter, and will cuts with anything you'd use for wood. It's also reasonably stiff, waterproof, and resistant to a wide variety of chemicals/solvents (so don't plan on gluing it).
I used one today as the base for an 8-cell 18650 (lithium ion) charger I threw together, and though I'd never want to take something like this on a plane, I'm quite happy with it.
To leave a comment below, sign in using Github.