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, ensuring both sides are coated.
03 - Layer the diced onion, red bell pepper, frozen corn, and black beans over the seasoned chicken.
04 - Pour 1 cup of enchilada sauce evenly over the vegetables and beans.
05 - Arrange half of the tortilla pieces over the mixture, covering as much surface area as possible. 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 setting for 4 hours, or until chicken is cooked through and tender when tested with a meat thermometer (reaches 165°F).
08 - About 20 minutes before serving, shred the chicken directly in the crockpot using two forks. Mix thoroughly to incorporate 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.