Combine warm water and sugar in a bowl until sugar dissolves. Sprinkle yeast over top and let sit for 5-10 minutes until foamy and fragrant.
Whisk together bread flour and salt in a large bowl. Add activated yeast mixture and stir with a wooden spoon until a rough, shaggy dough forms with no dry flour remaining.
Turn dough out onto a lightly floured surface and knead by hand for 8-10 minutes, or use a stand mixer with dough hook on medium speed for 6-8 minutes, until smooth, elastic, and slightly tacky.
Shape kneaded dough into a smooth ball, place in a lightly oiled bowl, and turn to coat. Cover and let rise in a warm spot for 1.5-2 hours until doubled in size.
Gently turn risen dough out onto a floured work surface. Divide into 2 or 3 equal pieces. Pat each piece into a rectangle, fold like a letter, then roll and stretch into a 14-16 inch log with tapered ends.
Place shaped loaves seam side down on a parchment-lined baking sheet dusted with cornmeal, leaving space between each. Cover loosely and let rise for 45-60 minutes until noticeably puffy.
About 20 minutes before baking, place an empty metal pan on the bottom rack and preheat oven to 475°F along with your baking stone if using. Uncover proofed loaves and score with a bread lame, making 3-4 diagonal slashes about 1/4 inch deep.
Lightly mist the tops of loaves with water. Quickly slide into the oven and pour about 1 cup of hot water or toss a handful of ice cubes into the preheated pan to create steam. Bake for 22-28 minutes until deep golden brown and hollow-sounding when tapped.
Transfer baked baguettes to a wire cooling rack and let cool for at least 20-30 minutes before slicing to allow the interior crumb to set properly.