01 - Lightly grease the inside of a 6-quart slow cooker with cooking spray or 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. Top with 1 cup of shredded Mexican cheese blend.
06 - Pour remaining enchilada sauce over the cheese layer. Add remaining tortilla pieces and top with remaining 1 cup of cheese.
07 - Cover and cook on low heat for 4 hours, or until chicken is cooked through and tender (reaches internal temperature of 165°F).
08 - About 20 minutes before serving, shred the chicken directly in the slow cooker using two forks. Mix thoroughly to combine all ingredients. Cover and let sit to meld flavors.
09 - Serve hot, garnished with fresh cilantro, sliced green onions, and a dollop of sour cream if desired.