01 - Lightly grease the interior of a 6-quart crockpot with cooking spray or a small amount of oil.
02 - Place chicken breasts in the bottom of the slow cooker. Sprinkle evenly with cumin, chili powder, garlic powder, salt, and pepper on both sides.
03 - Layer the diced onion, red bell pepper, frozen corn, and drained black beans over the seasoned chicken.
04 - Pour 1 cup of enchilada sauce evenly over the vegetable and bean mixture.
05 - Arrange half of the quartered tortilla pieces over the sauce. Sprinkle with 1 cup of shredded Mexican cheese blend.
06 - Pour remaining enchilada sauce over the cheese, top with remaining tortilla pieces, and finish with the remaining 1 cup of shredded cheese.
07 - Cover and cook on low heat for 4 hours, or until chicken reaches an internal temperature of 165°F and is tender enough to shred easily.
08 - About 20 minutes before serving, use two forks to shred the chicken directly in the crockpot. Stir thoroughly to incorporate all ingredients and let sit covered to meld flavors.
09 - Serve hot in bowls, garnished generously with fresh cilantro, sliced green onions, and a dollop of sour cream if desired.