I can make really good pizza in my normal home oven at 500 with a 1/2" steel plate as a cooking surface.
Go to a metal store, buy 2 pieces of 1/2" thick steel plate/bar in whatever width you can fit in there (1/2 depth of oven minus a little for the door to clear) and the length equal to width of your oven. Using 1 single large piece of metal would be cost prohibitive and too heavy to move in and out. I cleaned mine up slightly with a grinder then put some cooking oil on it to season it and keep it from rusting
Preheat for at least 30 minutes. Use a wood peel to slide the pizza right onto the metal. In my oven a pizza cooks in about 6.5 minutes.
Sure beats a dedicated appliance unless you're cooking pizza REALLY often.
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