I never put the stickers on because, unless you put the sticker on *perfectly* -- which ain't happening here -- it's not really going to help you stamp the image *perfectly.* If your sticker is just a smidge off and you use that image to place your stamped image, then your stamping is a smidge off. I'm perfectly capable of placing a stamped image a smidge off without the help of a sticker, thankyouverymuch.
I trim the rubber closely and look through the clear block and that's good enough most of the time. If placement is crucial, I use a Stamp-a-Ma-Jig (or whatever it's called).