The night before: Poolish

Whisk together the poolish ingredients until smooth in a jar or bowl with room to roughly double. Cover loosely and rest at room temperature for 12 to 14 hours, until bubbly, domed on top, and just beginning to flatten in the center. 

The next morning: Final dough

• Combine the flour with the water and the poolish. Mix until no dry flour remains. Cover and rest 30 minutes (autolyse).
• Sprinkle the salt and yeast over the dough. Mix in by squeezing and folding until fully incorporated, adding a splash of water if needed to dissolve the salt.
• Bulk ferment at room temperature 2.5 to 3 hours. Stretch and fold every 30 minutes for the first 1.5 hours (3 sets total). The dough is ready when smooth, slightly puffy, and well developed.
• Divide by weight (300g, 450g, and/or 550g). Preshape each piece into a rough log and rest, covered, 20 minutes.
• Shape to suit each size and set seam-side up in a well-floured 15-inch basket. 300g: a thicker 10 to 12 inch baton, centered with space at the ends. 450g and 550g: pat to a rectangle, letter-fold, seal, and roll into a long taper to fill the basket.
• Final proof. Same day: cover and proof at room temperature 45 minutes to 1 hour, until the dough springs back slowly when pressed. Overnight: cover well and refrigerate; bake straight from the fridge the next morning.
• Preheat to 475°F (245°C) for 45 minutes with a stone or steel and a cast iron steam pan below it.
• Turn out, score with one long shallow slash down the center, slide onto the stone, and add a cup of hot water to the steam pan.
• Bake 22 to 26 minutes, until deeply golden and 205 to 210°F (96 to 99°C) internal. Check the 300g loaf around 18 to 20 minutes.
• Cool on a wire rack at least 30 minutes before slicing.