1 1/2 cups (350 grams/12 ounces) tepid water (70 to 78 degrees)
1 teaspoon (5 grams/.2 ounce) instant yeast
3 1/4 cups (500 grams/17.6 ounces) unbleached all-purpose flour
1 1/2 teaspoons (10 grams/.4 ounce) sea salt or kosher salt
Pour the water into the bowl of a stand mixer. Add the yeast, flour, and salt and stir with a rubber spatula just until all the water is absorbed and a dry, clumpy dough forms. Cover the bowl with plastic wrap and let stand for 20 minutes, to allow the flour to absorb the water. Use the dough hook of a stand mixer and mix the dough on low speed (2 on a KitchenAid mixer) for 8 to 10 minutes. It will still be a little lumpy, although it will gather into a ball around the hook. Pull it off the dough hook and knead it by hand for a few strokes on an unfloured surface until it is very smooth and springy. (Alternatively, scrape the dough onto a lightly floured surface and knead with smooth, steady strokes until silky smooth and springy, 10 to 12 minutes. Avoid kneading extra flour into the dough.) Transfer the dough to a lightly oiled, clear, 2-quart straight-sided container with a lid. With masking tape, mark the spot on the container where the dough will be once it has increased 1 1/2 times in volume. Cover and leave it to rise at room temperature (70 to 75 degrees) for 45 minutes. It will increase by about 25 percent. Lightly dust a work surface with flour and, using a bench scraper or spatula, empty the risen dough out of the container. Pat it gently into a rectangle, about 6 x 8 inches, and fold it into thirds like a business letter. With the short side facing you, lift the top edge and fold it into the center of the rectangle; lift the near edge and fold it into the center so that it overlaps the top edge by about 1-inch. Quickly slide both hands under the dough and flip it over so the folds are underneath. Slip it back into the container, pushing it down to fit. Cover the dough and let it rise in a warm and draft-free spot until it expands, reaching halfway to the masking tape mark. 45 minutes to 1 hour. About 1 hour before baking, place a baking stone on the middle rack of the oven and a cast-iron skillet on the lower rack. Preheat the oven to 450 degrees. (If you are baking the breads on a baking sheet, its only necessary to preheat the oven about 20 minutes before baking.) Lightly dust your work surface with flour. Uncover the dough and turn it out onto the work surface. With a bench scraper or chefs knife, cut the dough into 3 equal pieces. Gently pat each piece into a rough rectangle and fold it in half. Sprinkle the pieces of dough with flour and lightly drape them with plastic wrap. Let them relax on the counter for 10 minutes. Cover a bakers peel or rimless baking sheet with parchment paper and lightly dust with flour. Set aside. On a lightly floured work surface, pat the dough into a rough rectangle measuring about 3 x 5 inches. With the longer side facing you, fold the top of the dough down about one-third of the way toward the center. With the heel of your hand, press along the seam using firm but gentle pressure. Fold the bottom of the dough about one-third of the way toward the center and seal the seam firmly. Fold this skinny rectangle in half, bringing the top edge down to meet the bottom edge. Working from right to left, cup your hand over the log of dough arid press the heel of your hand down firmly to seal the seam. Dust the work surface with additional flour to prevent the dough from sticking. To stretch the log, place your hands together, palms down, over the middle of the log. Using light, even pressure, roll the log back and forth as you spread your hands apart. Repeat 3 or 4 times until the log is the desired length, about 14 inches long. Leave the ends rounded. Place the baguettes on the parchment, seam sides down, about 2 inches apart. Lift the parchment between the loaves, making pleats and drawing the loaves together. Tightly roll two kitchen towels and slip them under the parchment paper on the sides of the two outer loaves to support and cradle the baguettes. Lightly dust the tops of the baguettes with flour and gently drape them with plastic wrap. Let the loaves stand at room temperature for 30 to 40 minutes. They will increase about 1 1/2 times in size. Uncover the loaves, take away the towels, and stretch the parchment paper out so it is flat and the loaves are separated. Score each baguette with a single-edge razor blade or a serrated knife. Starting from the tip, angle the blade 45 degrees to make 3 slashes about 3 inches long and 1/2-inch deep. Slide the loaves, still on the parchment, onto the hot baking stone or rimless baking sheet. Place 1/2 cup of ice in the hot cast-iron skillet and slide back onto the lower rack to produce steam. Bake the baguettes until caramel colored, 15 to 20 minutes. Slide the peel or baking sheet under the parchment paper to remove the loaves from the oven. Slide the loaves, still on the parchment, onto a wire rack to cool. Eat them warm or at room temperature. Freeze leftover baguettes in resealable plastic bags for up to 1 month.