In a large bowl combine flour, yeast, and salt. Add water and stir until blended; dough will be shaggy and sticky.

Cover bowl with plastic wrap. Let dough rest at least 12 hours, preferably about 18, at warm room temperature, about 70 degrees Fahrenheit (21 degrees Celsius). Dough is ready when its surface is dotted with bubbles.

Lightly flour a work surface and place dough on it; sprinkle it with a little more flour and fold it over on itself once or twice. Cover loosely with plastic wrap and let rest about 15 minutes.

Using just enough flour to keep dough from sticking to work surface or to your fingers, gently and quickly shape dough into a ball.

Generously coat a cotton towel (not terry cloth) with flour, wheat bran, or cornmeal; put dough seam-side down on towel and dust with more flour, bran, or cornmeal. Cover with another cotton towel and let rise for about two hours. When it is ready, dough will be more than double in size and will not readily spring back when poked with a finger.

At least a half-hour before dough is ready, preheat oven to 450 degrees Fahrenheit (230 degrees Celsius). Put a six- to eight-quart (five- and- a- half- to seven- and- a- half-liter) heavy covered pot (cast iron, enamel, Pyrex, or ceramic) in oven as it heats.

When dough is ready, carefully remove pot from oven. Slide your hand under towel and turn dough over into pot, seam side up; it may look like a mess, but that’s okay. Shake pan once or twice if dough is unevenly distributed; it will straighten out as it bakes.

Cover with lid and bake 30 minutes (add rosemary oil at this point if desired), then remove lid and bake another 15–30 minutes, until loaf is beautifully browned. Cool on a rack.

Place oil, garlic, and rosemary leaves in a baking dish and bake for about 30 minutes.

Remove from oven and cool to room temperature. Serve as dip for bread.