In a large mixing bowl, combine the all-purpose flour, salt, and instant yeast.
Add the warm water to the dry ingredients and stir with a wooden spoon or spatula until a sticky, shaggy dough forms.
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, until it has doubled in size and the surface is bubbly.
Lightly flour a clean work surface and turn the dough out onto it. Sprinkle the dough with a little flour to prevent sticking.
Gently shape the dough into a rough rectangle, then fold it into thirds like a letter. Turn the dough 90 degrees and fold into thirds again. Let the dough rest for 15 minutes.
Divide the dough into two equal portions using a bench scraper or knife.
Shape each portion into a baguette by flattening it gently into a rectangle, folding the long edges toward the center, and rolling it into a log about 14 inches (35 cm) long. Pinch the seams to seal.
Place the shaped baguettes seam-side down on a baking sheet lined with parchment paper and lightly dusted with cornmeal or flour.
Cover the baguettes loosely with a kitchen towel and let them rise for 45 to 60 minutes, until slightly puffy.
About 30 minutes before baking, preheat your oven to 475°F (245°C). Place a baking stone or inverted baking sheet on the middle rack and a shallow pan on the bottom rack.
Once the oven is hot, transfer the parchment paper with the baguettes onto the preheated baking stone or sheet.
Pour 1 cup of hot water into the shallow pan to create steam and quickly close the oven door.
Bake the baguettes for 20 minutes, then remove the steam pan and continue baking for another 10 minutes, until the crust is deep golden brown and crisp.
Remove the baguettes from the oven and transfer them to a wire rack to cool completely before slicing.