In a large mixing bowl, combine the flour, active starter, water, and salt.
Knead the dough well for 7-8 minutes by hand or 4-5 minutes in a machine until it becomes smooth and elastic.
Cover the dough with a damp cloth and let it rest in a warm place for 4 hours, or refrigerate it for 8-12 hours. If refrigerated, remove the dough from the fridge 3-4 hours before shaping to let it come to room temperature.
Divide the dough into 8 equal pieces, and form each piece into a ball. Cover with a damp cloth and let them rest for 45-60 minutes.
Preheat the oven to 500°F and place a pizza stone or an upside-down cookie sheet in the oven.
Roll out each ball into a circle that is 7-9 inches in diameter.
Bake the pitas for about 3-5 minutes on the preheated pizza stone or upside-down cookie sheet until they are puffy and lightly browned.
Remove the pitas from the oven and wrap them in a clean towel until ready to use.