Combine all the spice rub ingredients in a small bowl. Generously rub all over the flank steak. Place in the bottom of a slow cooker, top with the diced peppers and onions. Cover and cook on LOW for 6 to 8 hours.
Combine the Avocado Pico de Gallo ingredients in a bowl, and gently stir to combine. Cover and place in fridge until ready to use.
Once carne asada is done, use two forks to shred the steak (should fall apart very easily).
Place a pile of tortilla chips on a plate, cover with the hot carne asada, some shredded cheese, a nice helping of avocado pico, and some sour cream. Enjoy!