I have the same unit that PineConeDon illustrates above. I think I paid $43 for it at the Wallymarto in Ennis.
My
Casita salesman said to just put it on the carpet. That's where it is now, but I am going to put it on a coupla 1x2"s routed out for the wee feet so it doesn't slide around. I have plenty of room for mine, so I store clingfilm, alumafoil, and wax paper on top.
The issue, I think, is where does it vent and what does it need to breath. Most seem to use the bottom for that and so carpet placement might be a little iffy. That's why, despite my salesman's enthusiasm for carpet, I am going to lift it up a tad and create some breathing room under it.