Step 1: In a large bowl, whisk together the active starter and warm water until milky and combined.
Step 2: Add the bread flour and salt to the liquid mixture and stir with a spatula until a shaggy dough forms and no dry flour remains.
Step 3: Cover the bowl and let the dough rest for 30 minutes at room temperature.
Step 4: Perform 4 sets of 'stretch and folds' every 30 minutes. Pull the edge of the dough up and fold it over the center, rotating the bowl as you go.
Step 5: Cover and let the dough rise (bulk fermentation) in a warm spot until it has grown by about 50-75% in volume.
Step 6: Gently shape the dough into a round boule on a floured surface, creating tension on the top of the loaf.
Step 7: Place the dough in a floured proofing basket, cover, and refrigerate for 12-15 hours for a cold proof.
Step 8: Preheat a Dutch oven in the oven at 450°F (230°C). Score the loaf and bake with the lid on for 20 minutes.
Step 9: Remove the lid and bake for an additional 20-25 minutes until the crust is golden brown and the internal temperature reaches 208°F.
Step 10: Allow the bread to cool completely on a wire rack for at least 2 hours before slicing.