For the baked shells: If using fresh, soft tortillas, spray them with a little olive oil and bake them for 5-8 minutes on each side or until crispy. They will curl up a bit at the edges. This is fine. Let cool.
Layer each ingredient on top of the tostada shell. Start with guacamole, then add the warm carne asada, shredded cabbage, pickled onions, salsa, cheese, and radishes. Serve with additional toppings on the side.