Step 1

In a large bowl, whisk together the bubbly, active sourdough starter and the filtered water. Add the all-purpose flour and bread flour. Use a sturdy spoon or spatula to combine. The mixture will be wet and sticky. Sprinkle it with salt, and gently pinch it with your fingers. Cover with plastic wrap and let rest for 1 hour.

Step 2

After 1 hour, leave the dough in the bowl, and complete 4 sets of "stretch and folds." These will be completed in 30 minute intervals.

Step 3

Stretch and Folds:Wet your hands with water, and grab a piece of dough near the top of the bowl. Pull it straight up to stretch making sure not to tear the dough. Fold it over to the center of the dough and press down lightly. Repeat this on each side of the bowl and the bottom. You'll do this 4 times (think of the bowl in fourths or quarters). After completing a stretch and fold in each quarter of the bowl, that is a "set." Complete 3 more sets of stretch and folds at 30 minute intervals over the next hour and a half, and cover with plastic wrap between each.

Step 4

After completing all 4 sets of stretch and folds, cover the bowl with plastic wrap, and refrigerate for 8 hours or up to overnight. When you're ready to work with the dough again, remove it from the refrigerator, and allow it to come to room temperature, about 1 to 2 hours.

Step 5

When the dough has warmed a bit, pour it from the bowl onto an unfloured work surface. Lightly flour the dough, and wet your hands. Place your hands on opposite sides of the dough and gently turn to tighten the dough and form a ball. The dough should stick to work surface and provide traction. Let it sit for 20 minutes to rest. It will spread some, but if it flattens out, repeat the process to tighten it into a ball. Let it rest for an additional 20 minutes. While the dough rests, prepare a cloth lined banneton or glass bowl lined with a lightweight kitchen towel. Dust the banneton or bowl lightly with rice flour then set aside.

Step 6

After the dough rests, wet a bench scraper and gently wedge it under the dough. Transfer the dough to the prepared bowl, cover with plastic wrap, and transfer to the refrigerator to double in size. This usually takes about 2 to 4 hours depending on how lively the yeast is.

Step 7

When the double has doubled in size, adjust an oven rack to the bottom third of the oven. Place a large Dutch oven with lid on the rack, and preheat the oven to 450°. Cut a large piece of parchment paper and remove the dough from the refrigerator. Remove the plastic wrap from the bowl and lay the parchment paper over the top of the bowl. Carefully flip the bowl upside down, so the dough is now on the parchment paper. Use a bread lame or sharp knife to score the dough if desired.

Step 8

Very carefully place the parchment paper and dough into the hot Dutch oven. Cover with the lid and bake for 30 minutes. After 30 minutes, remove the lid and bake for an additional 15 minutes. Remove the bread from the oven and transfer to a wire rack to cool completely before slicing, about 1 hour.

Step 9

Store any leftovers in a plastic zip bag. The leftovers stay fresh for about 2 days.