1. Sprinkle yeast and sugar over 1/2 cup warm water in a large bowl. Stir, and set aside for 10 minutes until mixture is foamy. Add 2 cups warm water, 2 tablespoons olive oil, 2 cups flour, and 1 tablespoon salt; stir until smooth. Gradually incorporate 4 more cups flour, using your hands once mixture becomes too thick to stir. If dough is sticky, add some of the remaining flour.

2. Transfer dough to a clean work surface; knead until smooth and elastic, using any remaining flour if needed, about 10 minutes.

3. Place dough in a lightly oiled bowl, and cover with plastic. Set in a warm place to rise until doubled in size, about 1 1/2 hours.

4. Heat oven to 425 degrees. Transfer dough to an oiled 11-by-17-inch baking pan; press to form an even thickness. If dough shrinks back, cover with a damp towel; let rest 10 minutes before continuing. Once dough fills pan, cover with a damp towel; let rise 30 minutes, until doubled in size.

5. Use your fingers to make dimplelike indentations in dough. Drizzle with remaining 2 tablespoons olive oil, allowing oil to fill dimples. Brush with a pastry brush to distribute oil over top of bread. Sprinkle with salt and rosemary; place in oven. Toss a cup of ice cubes into bottom of oven to create steam. Bake until golden brown, about 30 minutes, opening oven as infrequently as possible to prevent losing steam. Remove bread from pan; cool on a wire rack.