Depends on many factors.
If you are a fat slug, you will not get much past 7 degrees of left-to-right slope, as your chubby leg will get in the way.
If the slope is right-to-left, the left skid hangs low anyway, a normal-sized you will get around 10 degrees. But when it gets a bit scary, slippery, lumpy-bumpy and wind-gusty, cut the slope back to 5 degrees or less.
And treat every landing as if it were a slope landing - nice and gentle, slowly down.