In a large mixing bowl, combine 500g of bread flour and 350g of water. Mix until no dry flour remains, creating a shaggy dough. Let it rest for 30 minutes (autolyse).

After resting, add 100g of active sourdough starter and 10g of sea salt to the dough. Mix well until fully incorporated.

Begin the bulk fermentation by covering the bowl with a damp kitchen towel. Let the dough rise at room temperature for about 4-6 hours, performing stretch and folds every 30 minutes for the first 2 hours.

Once the dough has risen and appears bubbly, gently turn it out onto a lightly floured surface. Divide the dough into two equal portions.

Shape each portion into a round loaf by folding the edges toward the center. Flip the dough seam side down and shape it by rotating it against the surface to create tension on the outside.

Place the shaped loaves seam side up in bannetons or proofing baskets. Cover them with a damp cloth and let them proof for 1-2 hours at room temperature, or for a more robust flavor, refrigerate overnight (up to 12 hours).

Preheat your oven to 450°F (230°C) during the final stages of proofing. If using a Dutch oven, place it in the oven while preheating.

Once fully proofed, carefully turn the loaves out onto a parchment paper-lined baking sheet or directly onto a piece of parchment if using a Dutch oven.

Use a sharp knife or razor blade to create your desired scoring patterns on top of the loaves.

If using a Dutch oven, carefully place the lid on and bake for 30 minutes, then remove the lid and bake for an additional 15-20 minutes until golden brown. If using a baking sheet, bake the loaves for 30 minutes or until golden and hollow-sounding when tapped on the bottom.

Once baked, remove the loaves from the oven and allow them to cool on a wire rack for at least 1 hour before slicing.