You can use the cardboard that the filter came in, you can use a plastic bag, you can use a soda bottle cut appropriately, you can use form-a-funnel shape forming funnel, you can use aluminum foil, etc. Me, I since relocated my oil filter to under the left rear passenger footboard and now just let it drop directly into the pan without any mess.
I have one for the oil and one for the tranny. They are clear, have a lid and a cap on the end of the tube and you can stop the flow. Got them cheap from Wal-Mart. I like them because you can put the lid on and cap off the tube and keep dust and dirt ou of the funnel when not in use.
what ever you use make sure the bike is leaning to the left I change mine on my lift table and the first time I did I had the bike straight up and the oil ran ut the back side of the funnel
I had been using a piece of aluminum flashing, it worked OK.
I picked up a form-a-funnel at NAPA and used it last fall. It worked better, easier to form into place.