Line a 3-1/2 or 4-quart slow cooker with a disposable slow cooker liner. Lightly coat liner with cooking spray. In the prepared cooker combine stuffing mix, raisins, and onion. In a medium bowl combine water, soup, and sour cream. Pour soup mixture over stuffing mixture in cooker; stir gently to combine.
Cover and cook on low-heat setting for 5 to 6 hours or on high-heat setting for 2-1/2 to 3 hours. Makes 8 to 10 servings.