In a large bowl, combine the filtered water and active sourdough starter. Stir until the starter is fully dissolved. Add the bread flour and mix until no dry flour remains and the dough looks shaggy. Cover and rest 30 minutes (autolyse).

Sprinkle the salt evenly over the dough. Wet your hands and pinch the salt into the dough, folding until fully incorporated.

Every 30 minutes for the next 2 hours, perform 4-6 stretch-and-folds: wet your hands, pull the dough up gently, and fold over the center. Rotate the bowl each time.

Cover the bowl and let the dough rise at room temperature (70-75°F) until doubled in size and bubbly, about 4-8 hours depending on your kitchen temperature.

Turn the dough onto a lightly floured surface. Gently fold the edges to the center to form a loose ball. Flip seam-side down and rest 15-20 minutes.

Flip the dough seam-side up. Fold the top third down, bottom third up, then roll or tuck into a tight boule or batard shape. Place seam-side up in a floured banneton.

Cover and place the banneton in the refrigerator for 8-12 hours overnight.

Place your Dutch oven inside the oven and preheat to 450°F for 30 minutes. Turn the cold dough out onto parchment paper and score a deep slash with a sharp lame.

Carefully lower the dough into the hot Dutch oven. Cover and bake 20 minutes. Remove the lid and bake another 25 minutes until deep golden and hollow-sounding when tapped.

Transfer the loaf to a wire cooling rack and cool completely for at least 2 hours before slicing.