1. Combine the Wet Ingredients: In a large mixing bowl, combine the active sourdough starter, warm water, sugar, and olive oil. Whisk gently until the starter is mostly dissolved and the mixture is well combined. The mixture should look milky and slightly frothy.

2. Add Dry Ingredients and Mix: Add the salt and 3 cups of the all-purpose flour to the wet ingredients. Use a sturdy spoon or a Danish dough whisk to mix until a shaggy dough forms and no dry streaks of flour remain. It will be sticky and a bit rough.

3. Knead the Dough: Turn the dough out onto a lightly floured surface. Gradually add the remaining 1 cup of flour, a little at a time, as you knead for about 5-7 minutes. The dough should become smoother, more elastic, and less sticky, though it will still be soft. You’re looking for a dough that springs back slightly when poked.

4. First Rise (Bulk Fermentation): Lightly grease the mixing bowl with a little olive oil. Place the dough back into the bowl, turning it once to coat. Cover the bowl tightly with plastic wrap or a damp kitchen towel. Let it rise in a warm spot (around 70-75F) for 8-12 hours, or until it has at least doubled in size and looks bubbly. An overnight rise on the counter is often perfect.

5. Shape the Boule: Gently turn the risen dough out onto a lightly floured surface. Carefully deflate it by pressing out the air. Shape the dough into a tight round boule by pulling the edges towards the center and pinching them together at the top, then flipping it over and gently rotating it to create surface tension.

6. Second Rise (Proofing): Lightly flour a proofing basket (banneton) or a bowl lined with a floured kitchen towel. Place the shaped boule seam-side up into the basket/bowl. Cover loosely with plastic wrap or a kitchen towel and let it proof for 1-2 hours at room temperature, or refrigerate for 4-12 hours for a slower, more flavorful proof. The dough should feel puffy and slightly jiggly.

7. Preheat Oven and Dutch Oven: About 30 minutes before baking, place a Dutch oven with its lid into your oven and preheat to 450F (230C). Heating the Dutch oven ensures a great crust.

8. Bake the Bread: Carefully remove the hot Dutch oven from the oven. Gently invert the proofed dough into the hot Dutch oven. If desired, score the top of the dough with a sharp knife or razor blade (a simple “X” or a single slash works well). Cover with the lid and bake for 30 minutes. Remove the lid and continue baking for another 15-20 minutes, or until the crust is deeply golden brown and the internal temperature reaches 200-210F (93-99C).

9. Cool Completely: Carefully remove the bread from the Dutch oven and transfer it to a wire rack. Let it cool completely for at least 1-2 hours before slicing. This is crucial for the crumb to set properly and for the best flavor and texture.