In a large bowl, add 500 grams of flour, 350 grams of room-temperature filtered water, ½ cup of active starter, and ½ tablespoon of salt.
I like to start mixing with a wooden spoon and finish off with clean hands. Give this a good mix. You don’t want to knead the dough; you want to combine all the ingredients together till there are no dry streaks of flour. The dough will be very sticky; you might be tempted to add more flour. But do not add more flour than what the recipe is asking for.
After a good mix, cover the dough with saran wrap, a damp towel, or a lid. You don’t want a tight seal on the sourdough. You still want some air to circulate into the dough to help ferment it. Yet you don’t want the dough to develop a hard crust either. Set your timer for 30 minutes to begin your stretch and folds.
Next, you will perform 3-4 sets of stretch and folds. Gluten relaxes over time, and this step will help to build up the gluten and give it strength and shape. I like to use wet hands for this. Place your hands under the sourdough, and with both hands stretch the sourdough up as far as it will let you. Be gentle not to rip the dough, then fold it over to the middle of the bowl. Repeat this process on all sides. Once you have stretched and folded all sides of the sourdough, cover it with a damp towel and let rest for 30 minutes.
Repeat the previous step 3 more times.
Let the dough rise for 10-12 hours or until it has doubled in size. This is called bulk fermentation.
Next, you are ready to shape your dough. Scrape the dough from the bowl onto a clean work surface. Shape the dough into a round ball by first folding it. To start, fold the left side of the dough over the center, then fold the right side over the center. Grab the top of the dough and fold over the center, then roll the dough down to the end. Using your hands or a bench scraper, push and pull the dough to create surface tension; this will help the dough hold its shape and spring up as it bakes.
Line a bowl or proofing basket with a towel and dust it with flour (or you can dust the proofing basket directly). Transfer the shaped dough to the bowl or proofing basket with the seam side up and smooth side down. Cover tightly with a towel or place in a plastic bag and refrigerate for 12-24 hours, or at least 1 hour if you're short on time. It does not need to rise anymore; it will double in size as it bakes. In my experience, refrigerating for 12–24 hours yields the best results.
Next day, preheat your oven to 450 degrees F.
Remove the sourdough from the fridge. Place a piece of parchment paper over the proofing basket or bowl and flip it onto the table to release it from the bowl.
Using a sharp knife, razor blade, or scoring tool, score the top of the loaf as you wish. I like to do one big slash down the left or right side of the dough or a simple X across the top. There are no hard-and-fast rules to follow when it comes to baking sourdough bread at home, remember?
Grab the edges of the parchment paper and transfer it into your Dutch oven. Cover and place into the hot oven. Set your timer for 30 minutes. Remove the lid and bake for an additional 20–25 minutes, or until the loaf is a deep golden brown color on top.
Once the loaf has finished baking, remove it from the Dutch oven and let it cool for at least 1 hour before cutting. Cutting the bread too soon while it’s still hot will give it a gummy texture.