In a large bowl, add yeast to warm water and let it sit for 5 minutes until bubbly. Sprinkle a large baking sheet with corn meal.
Add sugar, salt and olive oil to yeast and water. Add flour, starting with 4 cups. Dough may be mixed by hand or using a mixer until dough comes together and no longer sticks to the sides of the bowl; you will most likely need to add the 5th cup of flour. When dough no longer sticks to the bowl, knead it in the bowl for 3-5 minutes.
With floured hands, divide the dough into two equal pieces, form each into a ball and coat generously with flour. Place floured dough balls on prepared baking sheet 4-5 inches apart.
Using a serrated knife, slash a tic-tac-toe design on top of each ball of dough. Cover loosely with plastic wrap sprayed lightly with nonstick spray and let rise in a warm draft free place for 40-60 minutes, or until doubled in size.
Position oven racks to have one in the center of the oven and one below it. Place a rimmed metal baking sheet on the lower rack. Preheat oven to 500°F.
Uncover dough and place the baking sheet with the loaves on middle rack. Toss 3-4 ice cubes on the baking sheet positioned on lower rack and close oven door immediately. Adding ice to the hot oven will create steam that results in the rustic crust artisanal bread is known for.
Bake bread for 15-20 minutes, or until golden brown. Remove bread from oven and place loaves on a rack to cool.