Place the chicken breasts in the slow cooker. Pour chicken broth over top plus the can of Rotel tomatoes with green chiles (including the liquid) over the chicken. Add in the diced onions.

Sprinkle the taco seasoning mix evenly over top.

Cover the slow cooker and cook on low heat for 6-8 hours or on high heat for 3-4 hours. Cooking times may vary depending on your slow cooker, so check the chicken's internal temperature to ensure it reaches a safe temperature of 165°F.

Once the chicken is cooked and tender, use two forks to shred it directly in the slow cooker.

Preheat a skillet or griddle over medium heat and spray with cooking spray. Take one flour tortilla and spoon some of the shredded chicken on top.

Sprinkle a generous amount of shredded cheese over top. Fold the tortilla in half, pressing it gently to seal.

Place the folded quesadilla on the preheated skillet or griddle and cook for 2-3 minutes on each side, or until the tortilla turns golden brown and the cheese is melted and gooey. Repeat this process with the remaining tortillas and ingredients.

Cut the quesadillas into wedges and serve with your favorite toppings, such as sour cream, salsa, guacamole, chopped cilantro, diced onions, or any other desired garnishes.