Bubbles in the crust are caused by trapped moisture that expands when the crust is baked. Small bubbles can be left alone but the pizza must be watched during the cooking process in case very large bubbles form, as this can cause the cheese and other toppings to slide off the bubble. As they are forming, pop the large bubbles with a long-handled metal poker. To prevent severe bubbling, the fresh crusts and crusts formed from dough balls need to be docked before the pizza is sauced and topped. The parbaked crust has already been docked, if large bubbles typically form in your oven pop them as needed.