When making a whole, slow-cooker chicken, it's best to buy a better-quality chicken such as one from a farm stand. The flavor and texture of the bird will hold up best over the long cook time. Also, leaving the skin on during cooking will ensure that the chicken stays moist. If you have leftover chicken, use it for a chicken soup or in a chicken salad sandwich. For a beautiful presentation, serve the chicken surrounded by fresh sage leaves and roasted, halved lemons and garlic heads.