Mix the starter and water together in a large bowl with a fork or spatula. Add the flour and salt. Mix to combine, finishing by hand if necessary to form a rough dough. Cover with a damp towel and let rest for 30 minutes.
After 30 minutes, stretch and fold the dough. Start by grabbing a corner of the dough and pull it up and fold into the center. Turn the bowl and repeat until you’ve performed the folds 4 to 5 times. Let dough rest for another 30 minutes and repeat the stretching and folding action. If you have the time, I recommend doing this twice more for a total of 4 times in 2 hours.
First Rise, bulk fermentation - Cover the bowl with a damp towel and let it rise at room temperature for about 8 to 10 hours (70 degree room). The dough is ready when it has increased by 50% in volume, has a few bubbles on the surface, and jiggles when you move the bowl from side to side.
Coax the dough onto a lightly floured surface. Gently shape it into a round: fold the top down to the center, turn the dough, fold the top down to the center, turn the dough; repeat until you’ve come full circle. If you have a bench scraper, use it to push and pull the dough to create tension.
Line an 8-inch (20-cm) bowl or proofing basket with a towel or insert and dust with flour. Using a bench scraper or your hands, shape it again as described in step 4. Place the round into your lined bowl, seam side up.
Proof/second rise - Cover the dough and refrigerate for 1 hour or for as long as 48 hours. *The longer the dough proof, the more the gluten breaks down.
Place a Dutch oven or baking pot, with lid on, in your oven, and preheat your oven to 500°F. Cut a piece of parchment to fit the size of your baking pot.
Place the parchment over the dough and flip the bowl to release. Using the tip of a small knife or a razor blade, score the dough however you wish. Use the parchment to carefully transfer the dough into the preheated baking pot.
Lower oven temperature to 450ºF. Bake the dough for 35 minutes, covered. Remove the lid, lower the temperature to 425ºF and continue to bake for 10 – 15 minutes more. Cool on a wire rack for 1 hour before slicing.