I am GF and make pizza using polenta sliced very thin for the crust. It's very good! I cook it in grapeseed oil by itself for a while to brown it up some, flip it over, then add the toppings as for any pizza. I mean I grease the pan with grapeseed oil. Canola would work too. We eat it with a fork, it can't be picked up like a pizza slice. I call it "PizzaLenta" (Pizza-polenta). Check your spaghetti sauce for gluten, or use fresh tomatoes and herbs.
I have used grits instead of bread for many of our breakfast meals too. The nice thing is you get a little nutrition and fiber using corn instead of flour.