Prepare the carnitas in the slow cooker according to package directions (about 6 hours on low in the slow cooker with ½ cup water). When done cooking shred the pork.
Preheat your oven broiler. Spread tostada shells lightly with refried beans, sprinkle some shredded carnitas on top of the beans, and then top with a sprinkle of cheese. Place under the broiler for 3 to 4 minutes, watching to make sure they do not burn.
Top warm tostadas with whatever you desire, lettuce, tomato, guacamole.
GUACAMOLE
Just mix all of the guacamole ingredients together to prepare and fresh cilantro if you'd like. Enjoy!