Whisk flour, yeast, and salt together in a large bowl. Stir water and 1 tablespoon olive oil in a separate container. Combine thoroughly and cover. Let the dough rest at room temperature for 8-12 hours or refrigerate for 12-36 hours until tripled in size.

Transfer the dough to a floured surface. Stretch and fold it until smooth. Shape into a ball while keeping it slightly sticky.

Pour remaining olive oil into a 12-inch cast iron skillet, coating it thoroughly. Transfer the dough into the skillet and press gently into a disc shape. Cover and rest for 2 hours at room temperature.

Preheat the oven to 400°F (200°C). Use fingers to press dough to the skillet edges, rising slightly up the sides.

Sprinkle Parmesan over the dough edges. Add one-third of mozzarella, pizza sauce, remaining cheese, and the pepperoni.

Bake until crust is golden and cheese is melted, approximately 20-25 minutes.

Heat the skillet on stovetop at medium for 3-5 minutes to crisp the crust bottom.