Whisk together the flour, yeast and salt in a large mixing bowl. Add the water and stir until combined. Cover the bowl with plastic wrap and allow to sit at room temperature for 19 hours.
After 19 hours, turn the dough out onto a lightly floured work surface. Punch down the dough and turn it over onto itself a couple of times. Cover with a tea towel and allow to rest 15 minutes. After 15 minutes, shape the dough into a ball. Coat hands with flour, if needed, to prevent sticking. Sprinkle the tea towel with half of the cornmeal and lay the dough on top of it, with the seam side down. Sprinkle the top of the dough with the other half of the cornmeal and cover with the towel. Allow to rise for another 2 to 3 hours, or until the dough has doubled in size.
To bake indoors in the oven: While the dough is rising the second time, heat the oven to 450°F. Place a 4- to 5-quart Dutch oven in the oven while it preheats. Once the dough is ready, carefully transfer it to the hot Dutch oven. Cover and bake for 30 minutes. Remove the lid and bake until the bread reaches an internal temperature of 210 to 212°F, another 15 minutes. Transfer the bread to a cooling rack and let cool at least 15 minutes before serving.
Outdoor coals: Heat charcoal in a chimney starter until ash covers all of the coals. Place 20 to 24 coals on a Dutch oven table. Place a cooling rack (or other wire rack that is at least 2-inches high) directly over the coals. Set a 5-quart outdoor Dutch oven on top of this rack and allow to heat during the last 30 minutes of the second rise. Carefully transfer the dough to the Dutch oven and cover with the lid. Place 20 coals on top. Bake until the bread reaches an internal temperature of 210 to 212°F, about 45 minutes. Transfer the bread to a cooling rack and let cool at least 15 minutes before serving.