How to Make It
Make the carnitas: Cut the pork into 1-inch cubes, discarding any large chunks of fat. Place the pork in a Dutch oven or large saucepan. Add enough water to cover the pork by 1 inch. Add the orange zest and juice, garlic, onion, red pepper flakes, cinnamon, bay leaves, 2 teaspoons of salt and the cloves. Bring the water to a boil, then reduce to a simmer. Skim off any foam that forms on the surface. Simmer the pork, uncovered and stirring occasionally, until very tender, about 11⁄2 hours, adding small amounts of water if necessary to keep the meat submerged. Discard the orange zest, bay leaves and cinnamon. Continue cooking the pork until all of the liquid has evaporated. Increase the heat to high and fry the pork until crispy, about 10 minutes. Transfer to a plate and set aside.
Meanwhile, make the guacamole: Halve and pit the avocado and scoop the flesh into a bowl. Mash the avocado with a fork and stir in the onion and lime juice; season to taste with salt. Cover the bowl with plastic, pressing it onto the surface of the guacamole to prevent browning. Refrigerate until ready to use.
Make the tostadas: Preheat the oven to 400°F. Brush both sides of the tortillas with oil and sprinkle with salt. Arrange the tortillas in a single layer on a baking sheet. Bake until the tortillas are crisp and the edges are golden, about 15 minutes. Remove from the oven and set aside.
Arrange the tostadas on a large rimmed baking sheet. Place 1 slice of cheese on top of each tostada. Spoon some of the carnitas over the tostadas, followed by the pinto beans. Bake until the cheese has melted and the edges of the tostadas are starting to brown, 8 to 10 minutes. Remove from the oven and spoon the guacamole, salsa verde and creama over the top. Serve immediately.