Slow Cooker Bone Broth
You can skim the froth that forms at the surface of a stock as it cooks, but there's no real reason to do so. Do this only if you must have a clear broth. Otherwise, keep it in and garner the health benefits.
You can also remove the congealed fat that forms at the top when the stock is cooled. If the bones are from grass fed and pastured animals, the fat will be healthy for you. Your call.