my cham just laid her eggs in a 12x12x12 plastic storage container, filled with moist play sand. I bought the container from walmart, and the sand from home depot, but your regional walmart might sell it, as my region was small and had to phase it out.
she dug a hole just deep enough that if I peeked carefully, I could only see the tip of her crest. (she's a veil)
I was worried, because people say they need about 12 inches of sand, and mine only measured up to about 9 or 10 inches once wetted down, but she didn't seem to mind.
I have read that some people's chams chose to lay in the plant pot, and those are not always up to suggested size.