In a large bowl, combine 500g bread flour, 350g water, and 100g active sourdough starter; mix until no dry spots remain.

Cover the bowl and let the dough rest (autolyse) for 30 minutes at room temperature.

Sprinkle 10g salt over the dough and mix until fully integrated, strengthening the dough structure.

Cover and bulk ferment for 4–6 hours at room temperature, performing a stretch-and-fold every hour.

Once doubled in size, transfer dough to a floured surface and shape into a round or oval by tucking edges into the center.

Place shaped dough seam-side up in a proofing basket, cover, and proof for 1–2 hours until nearly doubled.

Preheat oven to 450°F (230°C) and place the Dutch oven inside for at least 30 minutes to heat through.

Carefully transfer dough to the hot Dutch oven, score the top, cover, and bake for 30 minutes covered, then 15 minutes uncovered until golden brown and internal temperature reaches about 205°F (96°C).