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.
03 - Layer diced onion, red bell pepper, frozen corn, and black beans over the seasoned chicken.
04 - Pour 1 cup of enchilada sauce over the vegetable and bean mixture.
05 - Arrange half of the tortilla pieces over the mixture. Top with 1 cup of shredded cheese.
06 - Repeat layering with remaining enchilada sauce, tortilla pieces, and remaining cheese.
07 - Cover and cook on low heat for 4 hours, or until chicken is cooked through and tender.
08 - About 20 minutes before serving, shred the chicken inside the slow cooker using two forks. Mix thoroughly to combine all ingredients and let sit covered to meld flavors.
09 - Serve hot, garnished with chopped cilantro, sliced green onions, and a dollop of sour cream if desired.