Salt and pepper the meat on all sides. Place in the crock pot.
Add diced onion, chilies, and garlic around the meat. Cover the meat in taco sauce. Cook on low for 4 hours (especially if pork as you do not want to overcook it).
The last 30 minutes, combine all ingredients to make the masa topping. Shred the meat and add it back into the crock pot with an additional cup of water. Top the meat with the masa mixture. Top the masa mixture with shredded cheese if desired (cogita or cheddar). Cover and allow to cook for 30 minutes to an hour.
Serve with pica de galo, sour cream, lime or cilantro.