In a small cup, mix 3 teaspoons of chili powder, 1 teaspoon of ground cumin (don't leave that out), 1 teaspoon of salt, 1/4 teaspoon of black pepper, 1/4 teaspoon of oregano and 1 tablespoon of dry onion flakes. Mix well and sprinkle both sides of the meat evenly as possible (no need to brown the meat!!)
Put the seasoned meat in the crockpot in single layer and top with a 4 ounce can of undrained mild green chile's (I use Ortega).
Cook on low for 6 hours or until they are fall apart tender (it really depends on how thick the meat is). Don't add any liquid.
The leftovers (sliced on the bias) made fantastic grilled beef and cheese subs.