Spray slow cooker with nonstick cooking spray.
Place chicken breasts in slow cooker (they can be frozen or thawed, it doesn't matter).
Pour Rotel and green chiles over chicken.
Place cream cheese on top.
Cover and cook on low for 6-8 hours or high for 3-4 hours.
Once cooked, shred chicken using a hand mixer or two forks and stir in with other ingredients in slow cooker until well combined.
Heat a skillet to medium-high heat.
Melt butter on skillet.
Place equal amounts of the chicken mixture on half of the tortillas, sprinkle on some cheese and place another tortilla on top.
Cook quesadillas for 2-3 minutes on each side, or until cheese is melted and tortillas are golden brown.
Cut into slices.
Serve with guacamole, sour cream, and salsa.