Level or a slightly forward incline would be best.
I have a lift in my garage an the floor slopes front to back 2 inches per 10 feet. So I always jack the back of my car up a little while draining the oil. Don't forget, you put 7 in the dry sump, start the car and then add the remaining quart.
PS. Don't forget, there are two drain plugs. One to the front and one to the side of the oil pan.