To be honest it is probably easier to buy pre-made pitas. Of course these taste much better once you perfect how to roll them.
Make the starter the night before. In a large bowl mix 1 1/4 tsp yeast with 2 1/2 cups warm water. Let yeast dissolve and begin to bubble. Add 2 1/2 cups unbleached white flour and mix well. The starter will be the consistency of thick batter. Cover with a wet towel and let ferment over night, or at least 5 hours.
Mix 3 cups flour and 1 1/2 tsp salt into starter and form a rough dough. Knead for 10 minutes adding more flour slowly until dough is smooth and still slightly tacky to the touch.
Heavily oil a bowl with olive oil and place dough in. Cover with a damp towel and let rise until doubled, about 1 1/2 hours.
Punch down dough and flour the counter.
Cut the dough into eight pieces.
Roll out each piece on a floured counter to 8″ round. Too small and the pita will separate poorly, too big and it will not separate at all.
Preheat the oven to 425 degrees. Dust a baking sheet with cornmeal and bake pitas for about 8-10 minutes. Remove pitas from oven and place on a plate covered with a towel. Continue rolling and baking all the remaining dough. Slice in half and serve warm or cold.