The recommended time to cook boneless, skinless chicken breast in a slow cooker on low is generally about 3 to 4 hours. The chicken is done when it reaches an internal temperature of 165 degrees Fahrenheit. Some sources suggest that it can be done often around 3 hours on low, but times can range up to 4 or more hours depending on the slow cooker and the size of the chicken breasts. Bone-in breasts typically require a slightly longer cook time of about 3.5 to 4.5 hours on low. It's important to check the internal temperature with a meat thermometer to ensure safety and doneness. Resting the chicken 5 to 10 minutes after cooking before slicing or shredding is also recommended for juiciness.