pre-heat well oiled cast iron skilled for 15-20 minutes at 450℉
once heated, carefully remove skillet from oven
pour the sourdough discard directly onto the skillet in the middle and lightly around the edges. Add a little at a time, depending on the size of your skillet you may need more or less. I eyeball this but about 1/2 cup - 1 cup should be right.
spread the discard around the entire bottom of the skillet and up the sides using the back side of the ladle or wooden spoon.
the discard begins cooking right away so moving quickly is key, continue gently pushing the discard around with the ladle to cover the bottom and get in all the the edges and crevices. repeat until the skillet is fully covered to form your pizza dough.
place in the oven for about 8-10 minutes until the edges look golden brown and the bottom of the dough looks mostly cooked through.
remove from oven and add your toppings
place back in the oven for about 12-15 minutes to cook your toppings/melt your cheese
remove from oven and allow to cool for a few minutes. Remove the whole pizza from the skillet using spatulas or forks. Place on a cutting board, cut, enjoy!