In a large mixing bowl, combine the bread flour, salt, and instant yeast. Stir to evenly distribute the ingredients.
Pour the warm water into the dry ingredients and mix with a wooden spoon or spatula until a shaggy, sticky dough forms. Ensure all flour is hydrated.
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. With floured hands, gently fold the dough over on itself once or twice to shape it into a rough rectangle. Do not knead.
Divide the dough into two equal portions using a bench scraper or knife.
Shape each portion into a baguette by flattening the dough into a rectangle approximately 8 inches wide, then folding the long edges towards the center, pinching to seal the seam. Roll gently to elongate to about 14 inches in length.
Place the shaped baguettes seam side down on a baking sheet dusted with cornmeal. Cover loosely with a kitchen towel and let rise for 1 to 2 hours, until puffy but not doubled.
About 30 minutes before baking, preheat your oven to 475°F (245°C) with a baking stone or heavy baking sheet on the middle rack and an empty metal pan on the bottom rack.
Just before baking, use a sharp knife or lame to make 3 to 4 diagonal slashes about 1/4 inch deep on each baguette.
Place the baguettes on the preheated baking stone or baking sheet. Pour 1 cup of hot water into the empty pan on the bottom rack to create steam and quickly close the oven door.
Bake for 20 to 25 minutes, rotating the baking sheet halfway through, until the baguettes are deep golden brown and sound hollow when tapped on the bottom.
Remove the baguettes from the oven and transfer to a wire rack to cool completely before slicing.