PreparationFor sponge: Place 1 cup lukewarm water in large bowl of heavy-duty mixer. Sprinkle 1 teaspoon yeast (reserve remaining yeast for dough) and 1/4 teaspoon flour over water. Let stand until yeast dissolves and mixture looks spongy, about 4 minutes. Add remaining flour and whisk until smooth; scrape down sides of bowl. Cover bowl with plastic wrap. Let sponge rest at room temperature in draft-free area overnight (about 12 hours; sponge will look bubbly). For dough: Add 1 1/2 cups lukewarm water, 2 teaspoons salt, 1 envelope yeast, and reserved remaining yeast to sponge, then add 6 cups flour, 1 cup at a time, beating with dough hook to blend after each addition. Continue to beat until dough is smooth, comes cleanly away from sides of bowl, and is only slightly sticky to touch, scraping down bowl occasionally, about 5 minutes. If dough is very sticky, beat in more flour, 1/4 cupful at a time. Scrape dough onto floured surface; knead into smooth ball. Brush inside of large bowl with oil. Add dough; turn to coat with oil. Cover bowl with plastic wrap; chill 6 hours, kneading dough down when doubled (after 2 hours). About 1 1/2 hours before baking, dust 2 baking sheets with flour. Turn dough out onto floured surface. Knead gently; shape into 16-inch log. Cut into 8 equal pieces. Knead each piece into smooth ball. Arrange 4 balls of dough on each sheet. Cover loosely with kitchen towels and let rise until almost doubled, 1 to 11/4 hours. If using pizza stone, place in oven. Preheat oven to 500&Deg;F for 45 minutes. Working with 1 dough ball at a time, dust dough with flour. Press into 5-inch round, then gently stretch and roll out to 9-inch round. If using pizza stone, sprinkle pizza peel or rimless baking sheet with cornmeal. If not using pizza stone, sprinkle large baking sheet with cornmeal. Place dough round on cornmeal; brush lightly with oil. Top as desired. Slide pizza onto stone or place pizza on baking sheet into oven. Bake pizza until sauce is bubbling and crust is crisp and brown, lifting edge of pizza to check underside, about 14 minutes. Test-kitchen tip:To speed things up, you can bake two pizzas at the same time. To ensure even cooking, be sure to reverse the position of the baking sheets after 8 minutes. Baking two pizzas at once may take longer than 14 minutes.