Combine the cornmeal, salt, and flour in a large bowl. Add the beaten egg and then add the water slowly while stirring constantly. Stir until smooth. Add a small amount of oil (just to grease it) to a 6-8 inch skillet and heat over medium heat. When the skillet is hot, add 1/4 cup of the batter to the middle of the skillet. Turn the skillet gently to distribute the batter evenly over the bottom of the pan. Let cook for 30-40 seconds and then, using a large spatula, flip the tortilla over to cook on the other side. Cook for another 30-40 seconds. Remove the tortilla to a paper towel and repeat with the remaining batter. Stack the cooked tortillas in between layers of paper towels. Let them cool completely then store in a plastic bag or container in the refrigerator.