01 - Lightly grease the inside of a 6-quart crockpot with cooking spray or a small amount of oil.
02 - Place the 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. Top with 1 cup of shredded Mexican cheese blend.
06 - Add the remaining 1 cup of enchilada sauce, followed by the rest of the tortilla pieces, and finish with the remaining 1 cup of cheese.
07 - Cover and cook on low heat for 4 hours, or until the chicken is cooked through and tender (reaches an internal temperature of 165°F).
08 - About 20 minutes before serving, use two forks to shred the chicken directly in the crockpot. Stir thoroughly to combine all ingredients and meld flavors. Cover and let sit until ready to serve.
09 - Serve hot, garnished with chopped fresh cilantro, sliced green onions, and a dollop of sour cream if desired.