Depends on how deep your substrate is. If its deep enough you can bury half the pot to make it as if it was broken, otherwise you break it (which can be hard to do and have the results you desire). You can also use plastic pots and cut them with scissors (they just don't weigh that much and may get pushed over or moved.
I use a hammer and very carefully start tapping a line in one one side - then the others. After it's weakened like that - it pretty much comes apart where I want - but I have had my share of lopsided ones too. I just dig them into the dirt more when that happens.
I use clay pot for my redfoot too but I did not cut it. I don’t know how, instead I decorated by adding some fake leaves. I glued the leaves with hot glue. "Q" seems to like it very much...sometime is hard to get her out...only foods can make her go out of her hide
Clay pots can be nice for smaller torts. If you soak it and keep it warm it will be nice and humid in there. They are better if you can make them darker inside- cover part of the opening, point them away from the light. etc.
You can also use a bigger pot turned upside down and break an opening in it for the tort to enter.
You can cut them with a fine-bladed hacksaw or Dremel cutting disk. If you just groove it good it will break on the line. It takes some practice and is usually a pain in the neck. It is easier to just pile some substrate around it.
A real good way to cut clay pots is to mark where you want to cut them with a permanant marker and them soak them fully submerged in water overnight. The next day you can take any good quality carbide or diamond tip cutting device (hand saw, tile saw, power saw) and carefully cut them. Don't force the blade into the material, just let it cut at it's own pace. I use a carbide tipped masonary blade on a hand held grinder. A dremel tool would work with the right disc on it, it would just take a lot longer.