In a large bowl, combine flour, active starter, warm water, and salt. Mix with a wooden spoon until a shaggy dough forms and comes together in a ball. Cover with a clean towel and let rest for 30 minutes.

After 30 minutes, perform 12–15 stretch-and-folds. Lift about ¼ of the dough, stretch it upward, and tuck it into the center. Rotate the bowl clockwise and repeat until you’ve gone around the dough 12–15 times. Cover and let rest 30 minutes.

Repeat the stretch-and-fold process two more times, resting 30 minutes between each round.

After the final stretch and fold, cover and allow the dough to rest until doubled in size, about 6–12 hours depending on room temperature.

Transfer dough to a lightly floured surface. Gently shape by turning it in 4 quarter turns to form a ball. Let rest 15–20 minutes.

Flip the dough over and pinch the edges into the center to tighten the surface. Place seam-side up into a floured bowl. Cover tightly with plastic wrap and refrigerate at least 12 hours or overnight.

Place a Dutch oven with lid into the oven and preheat to 500°F. Heat for 45 minutes.

Remove dough from refrigerator and place onto parchment paper. Lightly dust the top with flour. Use a sharp knife or razor blade to score the top as desired.

Carefully remove the hot Dutch oven. Lift the parchment and dough into the pot. Cover with the lid and return to the oven. Bake for 20 minutes.

Reduce oven temperature to 475°F. Continue baking covered for 15–20 minutes, until deep golden brown.

Remove bread and cool completely on a wire rack before slicing.