Slow Cooker Chicken Tinga Tostadas

boneless skinless chicken ((I used a combo of breast and thighs))

can whole peeled tomatoes

tomatillo (green salsa)

adobo sauce ((from a can of chipotle peppers))

sliced onions ((depending on preference))

minced garlic

bay leaf

salt and pepper

Tostada shells ((1 package))

can refried beans (optional)

Store bought guacamole (or homemade, optional)

Sour cream and cheese for topping (optional)