01 - Lightly grease the inside of a 6-quart crockpot with cooking spray or oil.
02 - Arrange chicken breasts in the bottom of the slow cooker. Sprinkle evenly with cumin, chili powder, garlic powder, salt, and pepper.
03 - Layer 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 cheese.
06 - Add remaining enchilada sauce, followed by remaining tortilla pieces, and finish with the remaining 1 cup of shredded cheese.
07 - Cover and cook on low setting for 4 hours, or until chicken registers 165°F and is fork-tender.
08 - About 20 minutes before serving, shred chicken directly in the crockpot using two forks. Mix thoroughly to combine all layers and let sit covered to meld flavors.
09 - Serve hot, garnished with fresh cilantro, sliced green onions, and a dollop of sour cream if desired.