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 with one at a time, fry the tortillas, turning once, until crispy, puffed in places and deep golden brown, about 1 minute per side.
Transfer the tostadas to a paper-towel-lined baking sheet to drain. Repeat with the remaining tortillas. Serve warm.