1. Prepare the Dough

1. Mix the Dry Ingredients: In a large mixing bowl, combine the flour, salt, sugar, and yeast. Whisk to ensure everything is evenly distributed.
2. Add the Rosemary and Parmesan: Stir in the chopped rosemary and grated Parmesan cheese. These will infuse the dough with flavor as it rests.
3. Add the Water: Gradually pour in the warm water and mix with a wooden spoon or spatula until the dough comes together into a sticky, shaggy mass. There’s no need to knead—just ensure there are no dry pockets of flour.
4. Cover and Rest: Cover the bowl with plastic wrap or a clean kitchen towel. Let the dough rest at room temperature for 12-18 hours. During this time, the dough will rise and develop bubbles, creating a light, airy texture.

2. Shape the Dough

1. Flour the Surface: Generously flour a clean countertop or work surface. Turn the dough out onto the floured surface, using a spatula to scrape it from the bowl.
2. Shape the Dough: Dust your hands with flour to prevent sticking, and gently shape the dough into a round ball. Avoid overworking it—handle the dough as little as possible to maintain its airy structure.
3. Prepare the Skillet: Grease a 10- or 12-inch cast-iron skillet with olive oil and sprinkle the bottom with cornmeal (if using) to prevent sticking.

3. Let the Dough Rest Again

1. Place the Dough in the Skillet: Transfer the shaped dough into the prepared skillet.
2. Second Rise: Cover the skillet loosely with a kitchen towel and let the dough rise for 30-45 minutes, or until it puffs up slightly.

4. Preheat the Oven

1. Set the Oven Temperature: Preheat your oven to 450°F (230°C). Place an oven-safe lid or aluminum foil on top of the skillet for the first part of the baking process.

5. Bake the Bread

1. Bake with the Lid: Bake the bread in the preheated oven for 20 minutes with the lid or foil on. This traps steam, helping to create a soft, airy interior.
2. Remove the Lid: After 20 minutes, remove the lid or foil and sprinkle the top of the bread with additional rosemary, Parmesan cheese, and flaky sea salt, if desired. Bake for another 15-20 minutes, or until the top is golden brown and the crust is crispy.
3. Check for Doneness: The bread is done when it sounds hollow when tapped on the bottom, or when the internal temperature reaches 200°F (93°C).

6. Cool and Serve

1. Cool the Bread: Remove the skillet from the oven and let the bread cool in the skillet for 5 minutes. Then transfer it to a wire rack to cool completely.
2. Slice and Enjoy: Slice the bread into wedges or thick slices and serve. This bread pairs beautifully with soups, stews, salads, or simply dipped in olive oil and balsamic vinegar.