Ball below or above your feet

Below: more knee bend in your stance to get down to the ball
Above: stand a little taller in your stance

I try to take more club and less swing focusing on good contact, and remember that the golf ball will move down the hill.

Exception: Golf balls sometimes forget these rules when I aim near boundaries, hazards, or trees.

Above feet: choke up on grip accordingly with the slope of the ground. Club up since you’re choking up on the grip.

Below feet: Bend knees more and/or spread feet more. Use more of an upper body swing. Consider clubbing up, since lower body won’t contribute much distance.