Preparation

• In a large bowl or stand mixer fitted with the dough hook, combine all ingredients and knead the dough until it’s satiny and smooth, about 15 minutes.
• Cover the dough and set it in a warm spot. Let it rise until about double its original size. (Depending on the ambient temperature and how active the starters are, this can take 8 to 12 hours.)
• Punch down the dough to release trapped air, divide it in half, and shape each half into a round loaf. Put the loaves on a peel that’s well-covered with cornmeal, cover them with a moist towel, and let them rise 4 to 6 hours, until the loaves have doubled in size.
• Put a clay pizza stone on the floor of the oven and heat to  500°F for at least 45 minutes. Five minutes prior to baking, take the stone off the floor, put it on the bottom rack of the oven, and put a rimmed baking sheet on the oven floor. Lower the heat to 425° F.
• Slash the top of each loaf with a razor blade, lame, or very sharp knife. Slide the loaves off the peel and onto the baking stone. As soon as the loaves are on the stone, pour 1 cup of water into the baking sheet and quickly shut the door so the steam doesn’t escape. Bake the loaves until the crust is very dark, about 50 minutes to 1 hour.