Make a fake rock cave/basking spot for a reptile cage.

Step 9 Seal it.

This is a very important step. Use a safe, low fume sealer such as Water Based Polycrylic sealer if possible. Shellac also works well but will leave it shiny. I actually ran out of polycrylic so I used shellac inside the cave and on the bottom where it wouldn't be seen.
Use your other brush and apply 3 coats of sealant, once again, making sure to get into every crack and crevasse. Sorry, no pictures here, cause there's not much to see while sealing. Once you've finished, let it air out for a few days, preferably with a fan blowing on it.