Here in Ohio, I don't hesitate to plant southwest hillsides if they have the right shade and undergrowth. In fact, one of my best patches is in such a spot.
While the other's are giving their perspective (with which I'll not argue at all), my perspective is that the slope is normally for drainage purposes. I've grown ginseng in raised beds for years on flat ground. Remember, ginseng doesn't care whether there are certain trees -only that there is enough of some elements and not too much of others in the soil. Ginseng doesn't care if it is under trees at all -as long as there is enough shade to keep the surfaces of the plant cool. And I'd also say ginseng doesn't care if it is on a hillside or flat -as long as the soil is loose enough to drain well, yet organic enough to maintain necessary moisture.
My advice for new folks is always start slow and put out as many test plots as you can to test different areas you have to plant. Then, when time comes to plant the whole area, you know where the best area is each year.