In a large bowl, combine the sourdough starter and water.
Add the flour and salt. Mix until no dry flour remains and a shaggy dough forms.
Cover the bowl and let the dough rest at room temperature for about 4 hours.
During the 4-hour resting period, perform 1–4 sets of stretches and folds. Wet your hands, stretch one side of the dough up, and fold it over itself. Rotate the bowl and repeat on all four sides. Space the stretch-and-folds about 30 minutes apart if performing multiple sets.
Once the resting period is complete, refrigerate the dough for 12–24 hours.
When ready to bake, place a Dutch oven or cast-iron pot in the oven and preheat to 550°F.
Remove the dough from the refrigerator and gently turn it onto a lightly floured surface.
Shape the dough into around loaf by folding the outer edges toward the center and rotating it to create surface tension.
Place the dough onto a piece of parchment paper. Lightly dust the top with flour and score with a sharp knife or bread lame.
Carefully transfer the dough into the hot Dutch oven using the parchment paper. Place a shallow pan of water on the bottom oven rack if desired.
Cover with the lid and reduce the oven temperature to 450°F.
Bake covered for 30 minutes.
Remove the lid and bake for an additional 10–15 minutes, or until deeply golden brown.
Remove from the oven and transfer to a cooling rack.
Cool for at least 20–40 minutes before slicing.