Add a liner to the crockpot.
Measure all ingredients.
Slice boneless, skinless chicken strips into 1" long strips.
Add chicken to a large mixing bowl and stir in taco seasoning, chili powder, salt and pepper. Marinate for 30 minutes or longer in the fridge.
Drain and rinse black beans.
Drain corn if canned corn is being used.
Chop red onion and peppers.
Add onion, pepper, black beans, green chilies, if using, and corn to the chicken.
Add 1/3 of the salsa OR enchilada sauce in the bottom of the crockpot.
Top with 5 corn tortillas.
Add 1/3 of the chicken mixture into an even layer.
Top with 1 C salsa.
Add layer of 1 C grated cheese.
Continue layers, ending with cheese.
Turn crockpot on low for 5-6 hours.
Serve with whichever toppings desired: sour cream, cilantro, frito chips, tortilla chips, and/or sliced green onions.