Depending on how far you have to go, the general approach is this:
You want your shoulders parallel to the slope. This will seem counter intutive at first...it will go too high you think, and yes, this will increase the loft of the ball out of the bunker. But what is the biggest mistake is that if you keep your shoulders parallel to level ground, you will slam the club into the bunker and the club will not have a chance to get under the ball, it will get stuck in the sand and the ball will go nowhere. So, tilt the shoulders back even with the slope, and swing along the slope. Depending on the severity of the hill and the length of the shot, adjust the club to use...PW to even as much as a 7i to get the ball to go further and fly lower.