In place of Hard Tostada Shells, use small corn tortillas. Heat the oven to 400 degrees F (200 degrees C), and place the tortillas on a baking sheet, bake for 5-10 minutes until crispy.
To heat flour tortillas, you can either microwave them for 10 seconds or warm them in the oven. To warm them in the oven; heat the oven to 350 degrees F (180 degrees C), and wrap a stack of tortillas in foil. Heat the wrapped stack in the oven for about 15 minutes.