Make the dough: Dissolve the active sourdough starter in water.
90 grams active sourdough starter, 226 grams water
Add the flour and salt to the water and mix until no dry flour remains, and the dough is cohesive.
360 grams all-purpose flour, 6 grams salt
Cover the bowl with plastic wrap and let the dough rest for 30 minutes.
Strengthen the dough: Inside the bowl, gently pick up the dough with your fingertips. Fold the dough over itself, give the bowl a quarter turn, and repeat.
Transfer the dough to a clean bowl, cover, and let it rest for 30 minutes.
Perform coil folds: Working inside the bowl, Pick up the center of the dough with your fingertips and gently lift it until the dough releases from the bowl. Lightly set the dough back down, tucking the ends under. Give the bowl a quarter turn and repeat. Cover the bowl and let the dough rest for 30 minutes.
Repeat the coil folding process two more times, resting for 30 minutes between each fold.
Bench rest: Let the dough rise untouched for 1 to 2 hours in a warm spot. The dough should be bubbly and doubled in volume before you move to the next step.
Pre shape: Turn the dough out onto a clean surface and flip it so the top of the dough during proofing is facing up again. Gently round the dough into a tight ball. Cover with plastic wrap or a damp tea towel and let the dough rest for 15 minutes.
Shape the dough: Lightly dust your work surface with flour and flip the dough over so the top is facing down. Gently flatten the dough into a rough rectangle.
Fold the bottom of the dough closest to you towards the center, then fold the left and right sides towards the center. Fold the top of the dough over itself.
Gently flip the dough over and round it into a tight ball. Transfer the dough to a proofing basket or a banneton dusted with rice flour with the seam side up.
Cold proof: Cover the dough with plastic wrap and place it in the refrigerator to proof overnight (at least 8 to 16 hours)