Seems like common sense. Coincidentally, upon viewing this thread, I'm preparing to crush up my H on my toilet seat cover (down of course...). I don't suggest this unless you are OCD w/ cleaning, as I am.
I also use mirrors, SOME hardcover books. Some ppl use dvd cases/cd cases but I find these are too flimsy. SO- find one of the many hard surfaces inevitably surrounding you.
I would crush my up plate or flat glass or mirror, i would never use the toilet seat or the tank to the toilet seat, to me its gross putting ya face down were you shit and piss, you can never get a toilet clean enough, lol