Mill your flour on a fine setting
Use a kitchen scale to measure your flour and water. In a medium size bowl, mix together your flour and water by hand until you have a shaggy wet dough. It will be very wet and lumpy at this point. Cover your bowl with a damp tea towel and let it rest for 1 hour. This is called the autolyse.
Reset your kitchen scale, add 200 grams of ripe sourdough starter. By hand, incorporate the starter into the dough, then let it rest for 30 minutes.
Reset your kitchen scale, add 25 grams of salt. By hand, fold in the salt until it is combined, then let it rest for another 30 minutes.
From here, perform one set of stretch-and-folds every 30 minutes over the course of 2 hours, totaling 4 sets.
Cover the dough with a damp towel or bowl cover in between sets and let it rest for 30 minutes before starting the next set.
Once these are complete, perform one set of coil folds on your dough every hour for 2 hours, two sets in total.
After the final coil fold, cover your dough with a damp towel or bowl cover. Place it in a warm spot to bulk ferment until it has risen slightly and is bubbly. This usually takes 2-4 hours, but if your kitchen is warm, it may take less time; if it’s cool, it may take longer. This step requires close observation.
After your dough has finished the bulk fermentation, gently turn it out onto a lightly floured surface. Use a bench scraper, or a knife, to divide the dough into two even sections.
Starting with the first loaf, begin the shaping. The goal here is creating surface tension.
Working with the edges of your loaf, stretch them out to "laminate" the dough on the floured counter into a large square. Make sure you stop before you see any ripping.
Fold the left and right sides of the dough toward the center. Starting from the bottom, roll the dough into a ball, then build surface tension by gently pushing the dough away, cupping the backside, and pulling it back while dragging against the counter. Make sure to be gently and stop before you see any ripping. Repeat 5-6 times until you have a tight ball.
Repeat with the second loaf, then let both rest for 30 minutes—this is the preshape.
After 30 minutes, repeat the process for the final shape. Place the loaves seam-side up in a floured baneton. If you don’t have a baneton, you can use a regular bowl lined with parchment for a similar effect.
Cover your baneton with something airtight and place it in the fridge. My personal favorite airtight bread cover is some cheap hair nets. Just trust me, they're incredibly convenient. But I have also stuck them in grocery bags in a pinch! You can also use plastic wrap.
Leave your loaves to fridge ferment for 1-2 hours. You can do less or more based on your schedule, I have done as little as 20 minutes, and as long as 12-16 hours. But I have found the best results when I let my loaves fridge ferment overnight for 12 hours.
When you're ready to bake your loaves, start by preheating two Dutch ovens to 500°F for one hour. Carefully transfer the loaves onto parchment paper, score the top with a bread lame with the design of your choice. I recommend at least 1 large score to allow the bread to rise, the rest can be decorative. Place it into the preheated Dutch oven with the lid on and place in the oven
Once the loaf is in the oven, immediately reduce the temperature to 475°F and bake for 25 minutes. After that, remove the lid, lower the temperature to 425°F, and continue baking for about 20 more minutes, or until you reach your desired crust color. Finally, remove the bread from the Dutch oven and place it on a cooling rack to cool completely
Leave the loaves on the rack allowing them to cool for two hours before slicing. About 2 hours