Oil filter changing ?

[BASHO]

Just changed my oil and filter and had a problem getting the oil out of the base of the filter holder, couldn't get it all --hadn't got enough rags to soak it all up---so I reasembled with some manky old crapy oil still in , it dosen't bother me overmuch as I'll be changing it again in a couple of days.
This can't be right leaving dirty oil behind , so what am I missing here :?: