Combine 500g bread flour, 350g water, and 100g active sourdough starter in a large bowl. Mix by hand or with a wooden spoon for about 2 minutes until no dry flour remains and you have a shaggy, rough dough.

Cover the bowl and rest for 30 minutes at room temperature.

Sprinkle 10g salt over the dough and use a wet hand to pinch and fold the dough over itself repeatedly for about 5 minutes.

Cover the bowl and let the dough rest for 30 minutes.

Perform a stretch and fold by grabbing one side of the dough, stretching it up, and folding it over the center. Rotate the bowl and repeat from all four sides.

Repeat this stretch and fold every 30 minutes for the next 2-3 hours, then let the dough rest undisturbed for the final 1-2 hours of bulk fermentation.

Check the dough when it has increased in volume by about 50-75% and jiggles slightly when you shake the bowl.

Gently pour the dough onto a lightly floured work surface and let it relax for 5 minutes.

Using a dough scraper, gently pull one corner of the dough toward the center, rotate the bowl a quarter turn, and repeat until you have a loose round shape.

Let it rest for 15-20 minutes before final shaping.

Flour the dough generously and flip it seam-side up. Gently press the dough into a rectangle about 8 inches wide.

Fold the top third down and press gently to seal. Fold the top edge down again and seal. Roll the dough tightly toward you until you have a long cylinder about 14 inches long.

Place the shaped baguette seam-side up in a banneton or a bowl lined with a floured kitchen towel. Cover and let proof at room temperature for 2-3 hours, or overnight in the refrigerator.

Preheat your Dutch oven at 500F for at least 45 minutes.

Carefully flip your proofed baguette onto parchment paper and score with a sharp lame or knife at a 30-degree angle.

Transfer the parchment and baguette into the hot Dutch oven and cover with the lid. Bake for 20 minutes covered, then remove the lid and bake for another 10-15 minutes.

Transfer the baguette to a wire rack and let cool for at least 30 minutes before slicing.