Mix flour and salt together. Rub shortening into flour with fingertips until mixture has a fine, even texture. Stir in water until dough forms. Knead on a floured surface until smooth, about 2-3 minutes. Wrap in plastic and let rest at room temperature for 20-30 minutes. Knead a few times and divide into 8 pieces (for 10" tortillas), or 12 pieces (for 8" tortillas). Roll each into a ball and cover with plastic to keep from drying out. Roll each ball out on a floured surface, turning over frequently. Stack between sheets of waxed paper.
Heat an ungreased heavy skillet over medium high heat until "a water droplet flicked onto it dances in tiny droplets". Place a tortilla in the pan and cook until the top is bubbly and the bottom is flecked with brown (about 30 seconds). Turn it over and cook the other side about 20 seconds. If it puffs up during cooking, just flatten it back down with the spatula. Cook the rest the same way. Tortillas can be refrigerated up to 3 days or frozen up to two weeks. Reheat before using.
