The general consensus for cooking raw chicken in a slow cooker on low is as follows:

• Boneless, skinless chicken breasts typically take about 2.5 to 3.5 hours on low to reach the safe internal temperature of 165°F. Some variations show it could be between 1.5 to 3.5 hours depending on size and crockpot model, but 3 hours is a common ideal time.
• Bone-in chicken pieces like breasts or thighs may need longer, around 4 to 6 hours on low.
• Whole chicken often takes 6 to 8 hours on low.
• It is important to use a meat thermometer to check that the internal temperature reaches 165°F to ensure the chicken is fully cooked.

Therefore, for raw boneless chicken breasts in a slow cooker on low, plan for approximately 2.5 to 3.5 hours, while bone-in or whole chicken takes longer, from about 4 to 8 hours depending on the cut and size. Check doneness with a thermometer to avoid over- or under-cooking.