Pour broth into pot. Wash potatoes and sit in the middle next to one another to use as a "trivet", sprinkle them with sea salt to season. Sprinkle sliced onion around them.
Set unwrapped frozen whole chicken on top of potatoes. (if wrapper is stuck, run it under warm water for 1 minute and it will loosen right up)
Close lid and set to low heat for 6-7 hours (for a 3.5-4 lbs., larger will take longer to reach safe internal temp of 165 degrees F)
Ideally if you can open lid halfway through and sprinkle on your seasonings of choice that is best to add flavor, at that point they will stick to the skin. At end of cook time check internal meat temperature in middle of chicken breast to ensure it is at 165 F and has clear juices.
If you want to crisp skin at the end, set your oven to broil high and spray the top of your chicken with olive oil. Remove the inner pot of your slow cooker (with the chicken, broth and potatoes still in it) and stick it right into your oven for 4 minutes or until golden brown.
Remove from oven, transfer chicken to a cutting board and let it sit and rest for 10 minutes. Slice and serve.