For my beardies' feature wall I used some 100mm foam sheeting that renderers use to clad houses. Chopped, pinned and glued pieces into place for the general shape then used coloured tilers grout to cover it, with a final texturing by flicking grout onto the surface. Dry-brushed some sandstone-coloured pond sealer and gave it a final coat of clear matte and it came up looking really quite good. Whole process took less than a day. Used to play war games so just applied the same techniques used in making war games terrain.
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