Due to food safety reasons, you should not cook a frozen whole chicken in the slow cooker. Make sure to thaw it out completely before cooking (see how to safely defrost meat for more info). The ideal way to defrost meat is in the fridge overnight. If you think your chicken is still a little frozen in the middle you will need to increase the cooking time. A small chicken (5 pounds or less) usually can defrost in 24 hours or less A large whole chicken can take 2-3 days to safely defrost in a refrigerator