You can cook raw chicken in the slow cooker if you want too and it's safe to do so.
Just don't overfill the slow cooker with raw chicken because the chicken may not cook fully in the slow cooker or cook fast enough to kill off the bacteria.
I like to cook the chicken first on in a pan and then put the cooked chicken into the slow cooker when the other food is about cooked and ready to eat.
But I have placed raw chicken directly into the slow cooker and it did eventually cook all the way but it takes longer to cook the chicken in the slow cooker than it does in a pan.
You should cut the chicken up into small pieces before putting it in the slow cooker so that the chicken cooks more evenly and better.
You can put the whole chicken and bone in the slow cooker but I prefer to remove the chicken meat from the bone first and then place it in the slow cooker which makes it cook better when I cook raw chicken in the slow cooker.