Preheat your oven to 350 degrees. Grease a glass baking dish with cooking spray.
Flatten your chicken with a rolling pin. Season the chicken with salt and pepper on each side. Pour 1/4 cup of the buffalo sauce in the baking dish, place the chicken in the dish, and top with the remainder of the sauce. Bake for 20 to 25 minutes or until the chicken is cooked through.
Toss the spinach, celery, and carrots. Top it with the cheese, chicken, and dressing.