In a large bowl, combine the sourdough starter and water. Mix until the starter is dissolved.
Add the all-purpose flour and salt, then stir until a shaggy dough forms.
Cover the bowl with a clean towel and let it rest (autolyse) for 30 minutes.
After resting, knead the dough gently on a floured surface for about 5-10 minutes until smooth and elastic.
Place the dough back in the bowl and cover it. Let it ferment at room temperature for 4-6 hours, folding the dough every hour to strengthen the gluten.
After bulk fermentation, shape the dough into a tight round loaf.
Place the shaped dough into a floured proofing basket or bowl, cover, and refrigerate overnight (12-16 hours) for slow fermentation.
Preheat your oven to 450°F (230°C) with a Dutch oven or baking stone inside.
Carefully transfer the dough onto parchment paper, score the top with a sharp knife.
Place the dough with parchment inside the preheated Dutch oven; cover and bake for 20 minutes.
Remove the lid and bake for an additional 20 minutes until the crust is deep golden brown and crisp.
Remove the bread from the oven and cool on a wire rack before slicing.
