Place the chicken breasts in the bottom of your slow cooker. Season them generously with salt, pepper, cumin, chili powder, and garlic powder.
Pour the enchilada sauce over the seasoned chicken. Make sure the chicken is well coated for optimal flavor infusion.
Tear the tortillas into strips and layer them over the chicken and sauce mixture.
Sprinkle black beans, corn, and diced bell peppers over the tortilla layer.
Continue layering with more tortillas, sauce, veggies, and shredded cheese.
Cover the slow cooker and set it on low for 6-8 hours or high for 3-4 hours.
Once cooked, shred the chicken right in the slow cooker, mixing it well with the other ingredients.
Let the casserole rest for a few minutes after cooking. Serve it hot, garnished with fresh cilantro, avocado slices, or a dollop of sour cream if desired.