Location: Full timer,,,at Lake Georgetown in central Texas for the winter.
Leave the stone there always. I myself have gotten four 5 inch unglazed tiles from The Home Depot. I butt them up to each other on the floor of the overn.....not under the burner, but the floor above the burner. Make sure you don't block the vent holes along th sides. They're there to prevent super hot spots that screw up the bottoms of what you're baking.
We have not been able to get a pizza stone yet, so this is what we have done to compensate - flip biscuits and baked items over half way through cooking, or place slightly crumpled aluminum foil on the bottom of the cooking sheet and put your baked goods on top. The air and insulation prevent burning.