1. Autolyse and Initial Mix: In a large bowl, combine the warm water and active sourdough starter. Stir until the starter is mostly dissolved. Add the bread flour and mix with a spoon or your hand until no dry streaks of flour remain. The dough will be shaggy. Cover the bowl with a damp cloth or plastic wrap and let it rest for 30 minutes to 1 hour. This “autolyse” step allows the flour to fully hydrate and gluten development to begin without the salt.

2. Adding the Salt and First Knead: After the autolyse, sprinkle the salt over the dough. Using wet hands, gently work the salt into the dough by squeezing and folding it for about 2-3 minutes. The dough will feel a bit stiffer initially. Continue to mix until the salt is fully incorporated.

3. Perform Stretch and Folds (Bulk Fermentation): Over the next 2-3 hours, you will perform a series of “stretch and folds.” For each set, wet your hands, grab a portion of the dough from one side, stretch it upwards, and fold it over itself towards the center. Rotate the bowl 90 degrees and repeat this action three more times until all four sides have been stretched and folded. Do this every 30 minutes for the first 2 hours, then every hour for the remaining bulk fermentation time. The dough should become noticeably smoother, more elastic, and increase in volume by about 30-50%. Look for bubbles forming on the surface.

4. Pre-Shaping the Dough: Gently turn the dough out onto a lightly floured surface. Divide it if making multiple loaves. Lightly dust the top of the dough with flour. Using a bench scraper or your hands, gently form the dough into a loose round or rectangle. Avoid pressing out too much gas. Cover with a damp cloth and let it rest for 20-30 minutes. This “bench rest” allows the gluten to relax, making final shaping easier.

5. Final Shaping for Structure: Lightly flour your work surface again. Gently flip the dough over. For a round loaf (boule), gently pull the edges of the dough towards the center, creating tension on the surface. Flip the dough seam-side up into a floured banneton or a bowl lined with a floured kitchen towel. Ensure the seam is tight to hold the shape.

6. Cold Proofing (Retardation): Cover the banneton with plastic wrap or place it in a plastic bag and refrigerate for 8-12 hours, or up to 24 hours. Cold proofing slows down fermentation, develops flavor, and makes the dough easier to score and handle. The dough should feel springy but not overly puffy when gently poked.

7. Baking in a Dutch Oven: Preheat your oven to 475 F (245 C) with a Dutch oven inside for at least 30-45 minutes. Carefully remove the hot Dutch oven. Gently invert the cold dough into the hot Dutch oven. Score the top of the dough with a sharp razor blade or knife (a single deep cut or a pattern). Cover the Dutch oven and bake for 20 minutes.

8. Finishing the Bake: After 20 minutes, remove the lid from the Dutch oven. Reduce the oven temperature to 450 F (230 C) and continue baking for another 20-30 minutes, or until the crust is deep golden brown and the internal temperature reaches 200-210 F (93-99 C). Transfer the loaf to a wire rack to cool completely for at least 2 hours before slicing. Slicing too early can compromise the crumb structure.