- 3 cups room-temperature water
- 2 1/2 teaspoons salt
- 1 cup sourdough starter
- 6 cups bread flour
- 1 tablespoon cornmeal, or more as needed
- Mix water and salt together in a very large bowl. Add sourdough starter and whisk vigorously to mix and aerate; stir in 3 cups bread flour until smooth. Stir in remaining 3 cups bread flour until dough is completely mixed.
- Cover bowl and set aside until dough is bubbly and increased in volume, 12 to 15 hours.
- Turn dough on to a well floured work surface using floured hands. Turn dough several times to cover with flour. Return dough to an oiled bowl and let rest until dough is doubled in size but not risen enough to collapse, 2 to 3 hours.
- Preheat an oven-safe, lidded Dutch oven (at least 8 quarts) in a 450 degrees F (230 degrees C) oven for 30 minutes.
- Carefully remove Dutch oven using oven mitts and sprinkle cornmeal into the bottom to prevent dough from sticking.
- Gently roll dough out of oiled bowl and into the Dutch oven; replace lid.
- Bake in the oven for 30 minutes. Remove lid and continue baking until crust is lightly browned, about 15 minutes more. Carefully tip loaf out onto a cooking rack to cool completely.