Instead of one big 1-inch grid, I printed out tiles (3x3) and then laser engraved holes in the back of the boards for 1x3 mm rare earth magnet. I am using 3 so that even with a slight warp the boards will not wobble (any three non-collinear points, there is exactly one plane. - that’s why three-legged stools don’t wobble)
all you need is a thin metal board - like an oil pan or a piece of flashing and you can config your dungeon however you want without the pieces scooting around

I have not decided whether I like them straight out of the Glowforge or with a little grey and black stain sponged on

I used 1/8 mdf

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