In a small bowl, mix chicken soup and sour cream. In another bowl, combine melted butter and crumbled Ritz crackers. Place chicken in the bottom of a slow cooker, pour the soup/sour cream mixture over it, and spread.
Sprinkle Ritz mixture evenly on top. Cook on low for 6-8 hours or high for about 4 hours. Serve chicken over pasta, mashed potatoes, rice, or as desired.