Mix 500 g bread flour, 325 g water, and 100 g active starter in a large bowl until no dry flour remains; let rest 30–60 minutes for autolyse.

Add 10 g salt and the remaining 25 g water; pinch and fold for about 5 minutes until salt is fully incorporated.

Cover and begin bulk ferment at about 75 °F for 3–5 hours, performing one set of stretch-and-folds every 30 minutes for the first 2 hours.

When dough has risen roughly 50 % and shows bubbles, turn it onto a lightly floured surface and divide into two equal pieces.

Gently flatten each piece into a rectangle, roll tightly into a log, and taper the ends to form 12–14 inch baguettes.

Place each baguette seam-side up in a banneton or floured towel-lined bowl; cover and proof 2–4 hours at room temperature or overnight in the refrigerator.

Preheat oven and Dutch oven to 500 °F (260 °C) for at least 45 minutes.

Carefully invert baguettes onto parchment, score with one long slash or three diagonal slashes at a 30° angle.

Transfer baguettes with parchment into the hot Dutch oven, cover, and bake at 500 °F (260 °C) for 20 minutes to generate steam.

Remove lid, reduce temperature to 450 °F (232 °C), and bake 20–25 minutes more until deep golden brown and internal temperature reaches 205–210 °F (96–99 °C); cool on a wire rack at least 30 minutes before slicing.