01 - Lightly grease the interior of a 6-quart slow cooker with cooking spray or oil.
02 - Place chicken breasts at the bottom of the cooker. Sprinkle evenly with cumin, chili powder, garlic powder, salt, and black 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. Top with 1 cup of shredded Mexican cheese blend.
06 - Repeat layering with remaining enchilada sauce, tortilla pieces, and remaining shredded cheese.
07 - Cover and cook on low heat for 4 hours, or until chicken registers 165°F internally and is tender enough to shred easily.
08 - Twenty minutes before serving, shred chicken directly in the cooker using two forks. Mix thoroughly to incorporate all ingredients, then 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.