Heat the oil in a small skillet over high heat until it bubbles immediately when you touch the edge of a tortilla to the surface. Working one at a time, fry the tortillas for 10 seconds on both sides. Carefully fold the tortilla in half with tongs. Press the bottom half of the tortilla into the oil and fry until deep golden brown and crispy, about 1 minute. Flip the tortilla and fry the other side, pressing it into the oil until deep golden brown and crispy, about 1 minute.
Transfer the taco shell to a paper-towel-lined baking sheet, standing upright, to drain. Repeat with the remaining tortillas. Serve warm.