Combine yeast, sugar, and 1 cup warm water in bowl of a heavy-duty electric stand mixer; let stand 5 minutes. Add 2 cups flour, oil, and salt to bowl, and beat at low speed, using dough hook attachment, 1 minute. Gradually add additional flour until dough begins to leave the sides of the bowl and pull together. (Note: The dough will take on a "shaggy" appearance as the flour is being added. When enough flour has been added, the dough will look soft and smooth, not wet and sticky or overly dry with a rough surface.)
Increase speed to medium, and beat 5 minutes. Cover bowl of dough with plastic wrap, and let stand in a warm place (85°), free from drafts, 30 minutes or until doubled in bulk. Punch dough down, and let stand 10 minutes.
Turn dough out onto a lightly floured surface; shape dough into a 12-inch loaf, and place on a lightly greased baking sheet. Cut 3 (1/4-inch deep) slits across top of dough with a sharp paring knife. (The slits release interior steam and prevent the loaf from blowing apart at the side.)
Bake at 400° for 16 minutes or until golden brown. Cool on a wire rack.
Herbed Focaccia: Proceed with recipe as directed, shaping dough into a ball instead of a loaf. Roll dough into an 11- x 14-inch rectangle on a lightly greased baking sheet. Press handle of a wooden spoon into dough to make indentations at 1-inch intervals. Drizzle dough evenly with 1 tablespoon olive oil; sprinkle evenly with 1 teaspoon dried Italian seasoning. Bake at 475° for 12 to 15 minutes or until golden brown.
Pizza Crust: Proceed with recipe as directed, shaping dough into a ball instead of a loaf. Roll dough into an 11- x 14-inch rectangle on a lightly greased baking sheet. Drizzle with olive oil, or spread with pesto or pizza sauce, and sprinkle with desired toppings. Bake at 475° for 20 to 25 minutes.