Sidehill Lie - Ball below stance

Classic Style:

Here you have to stand a bit closer and lower to the ball. Your swing plane will get steeper with less body rotation, that means you mainly swing with arms and hands. A sclice can happen very easily, so calculate that and aim more to the left and let the ball curve to the target.

Modern Style:

Take care for the same points as shown in the classic style, plus flare your toes a bit inside, same as you try to slide down a hill at skiing. So it's easier to get a lower balance point and stability.