Slow Cooker Chicken Enchilada Casserole

onion, chopped

garlic, minced

olive oil

red enchilada sauce

tomato sauce

salt and pepper,

corn tortillas

boneless chicken breasts, cooked & shredded or cubed (or 1 large can chicken, drained)

Ranch-Style beans, drained

Mexicorn, drained

grated Mexican cheese blend

(2-1/4 oz) can sliced black olives

sour cream and chopped cilantro, for serving