A craft store was going out of business near me, and I picked up several SceneORama kits for $1 each. One of the kits was this plaster rock making kit. I molded the rocks, then glued them to balsa wood squares and rectangles. I used the included paints to put several earth tone washes on them, then used watered down PVA glue to coat the bases with fine talus. When the water soaked into the wood, it caused them to warp. They flattened out, mostly, but I definitely should not have used balsa. Last, I added coarser talus (included in kit), more washing (and more wood curling), and vegetation.
I have often considered using something in my D&D games to show areas where characters cannot go due to rough terrain and other obstacles. So that’s what I’ll use these for…someday.