Step 1

To a large mixing bowl, add the flour, 537g water, and sourdough starter and mix with wet hands until no dry bits remain. Cover the bowl and let rest for 30 minutes in autolyse.

Step 2

(9:30 a.m.)Add the salt to the top of the dough and pour on the remaining 43g of water to help dissolve. Mix by hand until the salt is incorporated and the dough comes together in a single mass. Transfer to a bulk fermentation container and cover.

Step 3

(9:45 a.m. to 1:15 p.m.)At a warm room temperature, around 74-76°F (23-24°C), bulk should take about 3 1/2 hours. Give the dough four sets of stretches and folds during this time. The first two sets are at 15-minute intervals (10:00 a.m. and 10:15 a.m.) and the last two at 30-minute intervals (10:45 a.m. and 11:15 a.m.). Perform vigorous stretches and folds, as seen below, for the first 3 sets, then a gentle set for the last set. After the last set, let the dough rest for the remainder of bulk fermentation, covered.

Step 4

(1:15 p.m.)Gently scrape the dough out of the bulk fermentation container and divide it into two pieces. Using wet hands, preshape each piece into a loose round and let rest for 30 minutes, uncovered.

Step 5

(1:45 p.m.)Shape each piece of dough into a round (boule), then place the dough in proofing baskets.

Step 6

(2:00 p.m. to 9:00 a.m., the next day)Cover proofing baskets with reusable plastic and seal shut. Then, place both baskets into the refrigerator and proof overnight.

Step 7

(9:00 a.m., the next day)Preheat your oven with a baking surface or combo cooker/Dutch oven inside to 450°F (230°C).