In a very large bowl (around 6 quarts), combine the flour, salt, and yeast. Pour in the warm water and use a wooden spoon to bring everything together. The dough will look rough and sticky: that’s perfect. If it seems dry, splash in a bit more water; if it’s overly wet, sprinkle in a little flour. You don't need to knead this dough, but I will often mix this in a stand mixer and let the dough hook mix for a few minutes.
Loosely cover the bowl with plastic wrap and let it rest at room temperature for about 2 hours. The dough will rise and become bubbly. If you aren’t baking right away, you can refrigerate the dough for up to two weeks. Leave the plastic wrap loose and don’t punch the dough down; it will naturally deflate slightly in the fridge.
Scatter cornmeal over a sturdy baking sheet. Lightly flour your hands and the surface of the dough, then pull off roughly one-half of it. Dust the outside of the dough ball with a little flour so it’s easier to handle
Gently stretch and tuck the dough until you create a smooth round loaf—this only takes about 30 seconds. Place it on the prepared baking sheet. Let it rest, uncovered, for about 40 minutes (or 60–90 minutes if the dough came from the refrigerator). It should puff slightly.
Set one oven rack to the lower position and one in the center. Place a metal pan (not glass) on the lower rack to create steam. Preheat the oven to 450°F.
Dust the top of the dough generously with flour. Using a sharp knife, cut a few ½-inch-deep slashes: use any pattern you like.
Slide the baking sheet onto the middle rack, then quickly pour about 1 cup of hot tap water into the pan on the bottom rack. Close the door immediately to trap the steam. Bake for about 30 minutes, or until the crust is deeply golden.
Let the loaf cool completely on a wire rack before slicing.
