Make sourdough starter (active and bubbly) or use an active starter that has doubled in size after feeding
Mix dough: combine starter, water, and flour until no dry flour remains
Rest dough (autolyse) 20–60 minutes
Add salt and mix thoroughly until evenly distributed
Knead or use stretch-and-fold until dough is smoother and elastic (about 5–10 minutes kneading or several rounds of stretch-and-fold)
Bulk ferment at warm room temperature until dough expands noticeably and bubbles form (about 3–6 hours, depending on temperature)
Perform stretch-and-fold during bulk (about 3–5 sets, every 20–45 minutes)
Check readiness: dough should feel airy and jiggle slightly; it should have risen roughly 30–75% (varies by recipe and starter strength)
Pre-shape: gently shape into a loose round; rest 15–30 minutes
Final shape: shape into a tight boule or batard and place seam-side up in a floured basket or seam-side down on a floured surface (depending on your method)
Proof in the refrigerator (cold proof) 8–16 hours, uncovered or loosely covered
Preheat oven with a Dutch oven or baking stone to 450–500°F (230–260°C) for 30–60 minutes
Score the dough just before baking (use a sharp blade) with a single confident cut
Bake: transfer dough to preheated Dutch oven; cover and bake 20–30 minutes
Continue baking: remove lid and bake 15–25 minutes until deep golden brown
Cool on a rack at least 1 hour before slicing