In a large glass bowl, combine warm water and starter, stirring until fully dissolved. Add salt and flour and mix with your hands until a shaggy dough forms. Cover with a kitchen towel and let rest for 1 hour.
After resting, perform four gentle stretch-and-folds using wet hands. Rest for 20 minutes, and optionally repeat this process 2–3 more times over the next hour.
After the final stretch, shape the dough into a ball, cover it, and let it rise for 8–12 hours until it is springy and it bounces back when gently pressed.
Turn dough onto a floured surface, flour the top, flip, then pinch edges to the center like a sack. Flip again so the seams are down and shape into a tight ball.
Line a bowl or colander with a floured towel. Place dough seam-side into the bowl, cover, and rest at room temperature for 30 minutes. Then refrigerate for at least 1 hour.
Place a Dutch oven and lid inside your oven and preheat to 500°F for 1 hour.
Remove the dough from the fridge. Flip onto a parchment-lined baking sheet, flour top, and score with a razor or knife. Transfer dough to the hot pot using parchment as handles. Cover and bake at 500°F for 20 minutes.
Reduce oven temperature to 405°F and bake for 20 minutes or until the internal temperature is 195–205°F.
Use parchment and a spatula to lift the bread from the pot. Cool on a rack for at least 1 hour before slicing and serving.