Combine the warm water and yeast in a large bowl and stir with a fork to dissolve the yeast. Let stand for 3 minutes.
Add the cool water and sponge starter to the yeast mixture and mix with your fingers for about 2 minutes, breaking up the sponge. The mixture should look milky and slightly foamy.
Add the flour and salt and mix with your fingers to incorporate the flour, scraping the sides of the bowl and folding the ingredients together until the dough gathers into a mass. It will be wet and sticky, with long strands of dough hanging from your fingers. If the dough is not sticky, add 1 tablespoon of water.
Move the dough to a lightly floured surface and knead for about 5 minutes, until it becomes supple and fairly smooth. This is a sticky, wet dough; don't be tempted to add more flour to the work surface. Just dust lightly and use a dough scraper as necessary to loosen the dough from the table during kneading. Allow the dough to rest for 15 minutes, covered with oiled plastic wrap. (This rest period is the autolyse.)
Knead the dough 3 to 5 minutes, until it is stretchy and smooth, yet still slightly sticky. Shape the dough into a loose ball, place it in a lightly oiled bowl, and turn the dough in the bowl to coat with oil. Cover the bowl tightly with plastic wrap and let the dough rise at room temperature (75 to 77 degrees) for about 1 hour, or until the dough looks slightly puffy but has not doubled.
Place the dough in the refrigerator for at least 8 hours, or preferably, overnight to let it relax, develop flavor, and become more manageable.
Take the dough from the refrigerator and let it sit at room temperature for 1 to 2 hours, until it begins to warm up and starts to rise.
Flour a work surface well and gently dump the dough onto it. Divide the dough into three equal pieces, about 13 ounces each. Gently flatten one piece, pressing out some of the air bubbles, and stretch it into a rectangle. Fold the top third down and the bottom third up as if you were folding a business letter. Now form the loaf into a short baguette by rolling the dough over from left to right and sealing the seam with the heel of your palm. Fold the dough over about 1/ 3 of the way each time, seal the length of the loaf, then repeat. You want to gently draw the skin tight over the surface of the loaf while leaving some air bubbles in the dough.
Seal the seam, being careful not to tear the skin of the dough or deflate its airy structure. Do not elongate. These loaves are about 10 inches long. Cover an area on the work surface with a thick layer of flour and place the loaf, seam side down, on the flour. Repeat with remaining pieces of dough. The loaves will be loose and slightly irregular in shape. Leave plenty of space between the loavesthey will spread as they rise. Cover the loaves with well oiled plastic and let them rise for 1 to 2 hours, until bubbly and loose.
Thirty minutes before baking, preheat the oven to 475 degrees. Place a baking stone in the oven to preheat and position an oven rack just below the stone.
Sprinkle a peel very generously with cornmeal. Line an upside down baking sheet with parchment paper and sprinkle very generously with cornmeal. Lift one loaf, flip it over so the floured side is on top, and gently tug on the ends to stretch the loaf to the full length of the peel, or about 14 inches on a pan. Repeat with the remaining loaves, placing 2 on the peel and 1 on the pan. Dimple each loaf with your finger in about 6 places, but don't deflate them too much. Be sure the loaves are loosened
continued in part 2