The evening before baking, combine 25 grams mature starter with 75 grams flour and 75 grams warm water at 90°F in a clean jar. Mix thoroughly until no dry flour remains. Cover loosely with plastic wrap and allow to rest at room temperature for 8-12 hours until doubled in size and bubbly.

The next morning, mix 100 grams ripe starter with 300 grams warm filtered water (90°F) in a large bowl until fully dispersed. Add 500 grams bread flour and 10 grams sea salt. Stir until a shaggy dough forms, then use your hands to bring it into a sticky ball.

Cover the bowl with plastic wrap and place it inside the oven with only the light on for warmth (~80-85°F). Let the dough rise for 5-6 hours until it visibly puffs up and doubles in size.

Lightly flour your counter and turn the dough out smooth side down. Fold the dough’s edges toward the center, pinching to seal. Repeat the fold sequence once more. Flip dough seam-side down and use cupped hands to rotate and tighten into a smooth ball.

Dust a bread basket generously with flour. Place the shaped dough seam-side up in the basket, lightly flour the surface, cover with plastic wrap, and return to the oven light for 2-3 hours until doubled and airy.

Remove dough from oven and preheat oven to 450°F. Place a sheet of parchment paper on counter and gently turn dough out seam-side down. Score the top with a sharp knife ½-inch deep lengthwise.

Using the parchment, lift the dough into the Dutch oven. Cover with the lid and reduce oven temperature to 425°F. Bake covered for 40 minutes, then remove the lid and bake an additional 5-10 minutes until the crust is dark golden brown.

Remove the bread from the Dutch oven with the parchment paper and transfer to a cooling rack. Let cool completely for at least 2 hours.