Leavened with a sponge starter, above, these free-form loaves are crusty and have a moist, chewy crumb.

Stir together well in a medium bowl:

Cover the bowl tightly with plastic wrap and let rise at room temperature (about 70°F) until bubbling and tripled in volume, 5 to 6 hours; or let rise for about 14 hours in the refrigerator.

Pour the sponge into a large bowl or a stand mixer fitted with the dough hook. Stir in:

Mix until the dough cleans the sides of the bowl. If necessary, adjust the consistency by adding flour or water. The dough should feel sticky to the touch but should not actually stick to your hands. Cover and let the dough rest for 20 minutes. Knead the dough on a lightly floured surface or with the mixer on medium-low speed until smooth and elastic, about 10 minutes.

Transfer the dough to an oiled bowl and turn once to coat with oil. Cover and let rise until doubled in bulk, about 3 hours in a warm place (75° to 80°F) or about 6 hours at cooler room temperature.

Divide the dough in half for round loaves or into 3 pieces for baguettes. Preshape each piece into a ball, cover, and let rest for 15 minutes. Shape the dough into round loaves or baguettes (for baguettes, follow the shaping instructions in Quick French Bread). For round loaves, transfer them bottom side up to floured bannetons if you have them. Otherwise place the shaped loaves on a parchment-lined baking sheet. Cover with plastic wrap and let rise at room temperature until doubled in bulk, 1 ½ to 3 hours.

Position racks in the center and lower third of the oven. Place a metal baking pan or cast-iron skillet on the lower rack. Preheat the oven to 450°F. If using a baking stone or steel, preheat it on the center rack for 45 minutes.

For round loaves, turn them out of the bannetons, if using, onto the preheated baking stone or steel or a parchment-lined baking sheet. For baguettes, if using a baking stone or steel, slide them with their parchment onto the stone or steel; or, simply bake them on the baking sheet they rose on. Score the tops of the risen loaves. Place the loaves on the center rack. Pour 2 cups boiling water into the preheated pan on the lower rack. Bake until the loaves are browned, the bottoms sound hollow when tapped, and the internal temperature reaches 210°F, about 35 minutes for baguettes, or about 40 minutes for round loaves. To further set the crust, turn off the oven and leave the baked loaves in the oven for 5 minutes.

Let cool completely on a wire rack.