Any design student will be intimately familiar with “foamcore board” or just “Foam core.” It’s a layer of plastic foam, usually slightly less than a quarter inch, sandwiched between two layers of slick paper.
It’s used for making 3D models; you cut it at an angle and fold.
Most foam core is white outside, white inside. They make black-on-black foam core. But what I really need at the moment is white-on-black foam core– black foam, white outside.
Eh yeah. I guess I’ll just take a Sharpie to the edges.