When I made mine, I put like 5 layers of tile grout (let dry overnight between applications), then 5 layers of polyurethane (non-toxic kind and let that dry overnight between applications). After the second to last application of polyurethane, I waited about 10 minutes, then "threw" colored sand at it. Waited about a half hour, and vacuumed excess sand off. Let that dry overnight, and repeated the same tomorrow, with a final layer of polyurethane over the sand. I made sure that every area of the tile grout was covered with the colored sand. I then let it dry outside for almost 2 weeks. Even though the poly I used said it is non-toxic, I wasn't taking any chances. You will need a good thick layer of tile grout (which is basically cement), as you want to make sure you do not miss the nooks and crannies, and you want to make sure there is enough on there so your beardies cannot get through to the polystyrene/styrofoam. Here is my enclosure (not completed in the pic, but it is now):

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