I have a stone that is as big as my oven shelf, so I just keep it in there. If I have refrigerated sauce, I microwave it for 2-3 minutes to get it warm/hot. ANYTHING refrigerated is a no-no to put on a stone. Likewise, putting a 500-800 degree stone on anything, save a elevated wire rack, is going to break it. Even if I get a frozen pizza, I put it on a triple folded sheet of foil and directly on the stovetop burner, let it flame for 10-15 seconds, turn it off, the repeat 4-5 times. This usually get the bottom thawed and hot enough to be able to place it on a stone. Microwaving a whole pizza, if it even fits, just gets it soggy, and not warm. Just use a peel and take the whole pizza out and place on a countertop.