My OC's are done in my driveway or garage, both of which have very light declines rather than flat and I have always appreciated that about them. Satisfies my brain a little with thinking it gets virtually all of the old oil out. I normally let the initial drain drip until it nearly doesn't anymore, lightly finger tight the pan bolt, remove the old filter (if it's time), clean up that mess, put new filter on, move the container back under the pan, remove the bolt again and normally have a little more oil come out. Let that get to a very slow drip again and then normally would move to the steps of refilling with the new, but like I said, figured since I wasn't going to use the spare jugs with a quart or two in them for anything else, I did the "pan flush". If no one takes the few leftovers I still have, I may do it the next couple OC's until gone. Once they're gone, though, I won't be continuing that step any longer.I think you'd be better served to position the vehicle with the drain at the lowest point possible in relation to the engine. Some of my cars that means having one side higher than the other, some it means to have the front end up higher than the rear. Then I let it drain until it's no longer dripping enough to care about (while I empty the oil into a recycling container, get it ready to be taken to be recycled, put the oil filter remover up, cut open the filter if I'm going to do so, etc.). Pouring in the fill-hole and having that oil bypass all the oil galleries, etc., and just draining out the drain seems impractical and not making a positive impact on the goal of an oil change: to replace MOST of the oil with new oil.