In a large mixing bowl, combine the all-purpose flour, instant yeast, and salt. Stir to mix evenly.
Pour the warm water into the dry ingredients and stir with a wooden spoon or spatula until a shaggy dough forms. The dough will be sticky and rough.
Cover the bowl tightly with plastic wrap or a clean kitchen towel and let the dough rest at room temperature for 12 to 18 hours, until the surface is dotted with bubbles and the dough has doubled in size.
Lightly flour a work surface and turn the dough out onto it. Sprinkle the dough with a little flour and fold it over on itself once or twice. Shape it gently into a ball.
Place a large piece of parchment paper on a kitchen towel and dust it with cornmeal or flour. Transfer the dough seam side down onto the parchment paper. Cover with a clean towel and let it rest for 1 to 2 hours, until it has nearly doubled in size.
About 30 minutes before baking, place a heavy covered Dutch oven or oven-safe pot with a lid in the oven and preheat to 450°F (230°C).
Carefully remove the hot Dutch oven from the oven. Using the parchment paper, lift the dough and place it into the pot. Cover with the lid.
Bake covered for 30 minutes.
Remove the lid and bake for an additional 15 minutes, until the loaf is deep golden brown and crusty.
Carefully remove the bread from the pot and transfer to a wire rack to cool completely before slicing.
Repeat the shaping and baking steps for the second loaf.