1. Autolyse (Initial Hydration): In a large bowl, combine the strong bread flour and 350 grams of the filtered water. Mix until no dry flour remains. The mixture will be shaggy. Cover the bowl and let it rest for 30-60 minutes. This step allows the flour to fully hydrate and gluten development to begin without the presence of salt or starter.

2. Incorporate Starter and Salt: After the autolyse, add your active sourdough starter and the fine sea salt to the dough. Using wet hands, gently incorporate them into the dough. It might feel a bit messy at first, but keep mixing until everything is well combined. If your dough feels too stiff, you can gradually add the remaining 25-50 grams of water, a tablespoon at a time, until the dough feels more pliable and sticky.

3. First Set of Stretch and Folds: After mixing, let the dough rest for 30 minutes. Then, perform your first set of stretch and folds. With wet hands, grab a portion of the dough from one side, stretch it upwards, and fold it over itself towards the center. Rotate the bowl a quarter turn and repeat this process 3-4 times until you’ve worked your way around the dough. This builds strength.

4. Repeat Stretch and Folds: Repeat the stretch and fold process every 30-45 minutes for a total of 3-4 sets during the bulk fermentation. As you perform each set, you’ll notice the dough becoming smoother, more elastic, and holding its shape better. It will start to develop a windowpane effect, meaning you can gently stretch a small piece of dough thin enough to see light through it without it tearing.

5. Bulk Fermentation (First Rise): After the final set of stretch and folds, cover the bowl and let the dough continue to ferment at room temperature until it has increased in volume by about 30-50%. This can take 2-4 hours after the last fold, depending on your room temperature and starter activity. Look for small bubbles on the surface and a jiggly, aerated texture.

6. Pre-Shaping and Bench Rest: Gently turn the dough out onto a lightly floured surface. Using a dough scraper, gently shape it into a loose round or rectangle. Avoid deflating the dough too much. Cover it with a clean kitchen towel and let it rest for 20-30 minutes. This allows the gluten to relax, making the final shaping easier.

7. Final Shaping: Lightly flour your hands and the dough. Gently shape the dough into your desired final shape (round or oval) with tension. The goal is to create a tight skin on the outside of the dough.

8. Cold Proofing: Carefully transfer the shaped dough into a floured banneton or a bowl lined with a floured kitchen towel, seam-side up. Cover it tightly with plastic wrap or a shower cap and refrigerate for 8-12 hours, or up to 24 hours. Cold proofing slows down fermentation, develops flavor, and makes the dough easier to handle.

9. Baking: Preheat your oven with a Dutch oven inside to 475 F (245 C) for at least 30 minutes. Carefully remove the hot Dutch oven, invert the cold dough into it, and score the top with a sharp blade. Cover and bake for 20 minutes. Remove the lid, reduce the oven temperature to 450 F (230 C), and bake for another 20-30 minutes, or until the crust is deep golden brown. Let it cool completely on a wire rack before slicing.