In a large mixing bowl, whisk together the all-purpose flour, salt, and instant yeast until well combined.
Pour the warm water into the dry ingredients and stir with a wooden spoon or spatula until a shaggy, sticky dough forms and all the flour is hydrated.
Cover the bowl tightly with plastic wrap or a clean kitchen towel and let the dough rest at room temperature for 3 to 4 hours, or until the surface is dotted with bubbles and the dough has doubled in size.
Lightly flour a clean work surface and turn the dough out onto it. Sprinkle the dough with a little flour to prevent sticking.
Using floured hands, gently fold the dough over itself 2 to 3 times to shape it into a rough rectangle. Divide the dough into two equal portions using a bench scraper or knife.
Shape each portion into a baguette by gently flattening it into a rectangle about 8 inches long, then folding the long edges toward the center and rolling it gently to form a tight cylinder about 12 inches long.
Place the shaped baguettes seam-side down on a baking sheet lined with parchment paper and dusted lightly with cornmeal or flour. Cover loosely with a kitchen towel and let rise for 45 minutes to 1 hour until puffy.
About 30 minutes before baking, preheat the oven to 450°F (230°C). Place a shallow pan on the bottom rack of the oven.
Using a sharp knife or razor blade, make 3 to 4 diagonal slashes about 1/4 inch deep across the top of each baguette.
Place the baking sheet with the baguettes on the middle rack. Pour 1 cup of hot water into the shallow pan to create steam and immediately close the oven door.
Bake the baguettes for 20 to 25 minutes until golden brown and crusty. The bread should sound hollow when tapped on the bottom.
Remove the baguettes from the oven and transfer to a wire rack to cool completely before slicing.