our group did this spinner card at our last stamp camp for 180 people. what we did was took some time before the workshop to mark on our fiskars slide cutters where they would have to line up the paper to make the correct cuts. we used tape on the cutter and pens to make the little marks. so in all there were 4 marks. two on the clear ruler indicating the "starting point" of the slit, and one indicating the ending point. we explained that they were using the little arrow on the orange cutting blade to line up with the hash marks on the tape. it was important to be fairly accurate.
on the edge of the cutter that tells you the measurements of your cut (i.e. 4 1/4", 5 1/2"), we decided where we wanted to start, made our mark, then made the 2nd mark 1/2" from the first. so they just slid the paper over, then ran the blade down. (they do NOT take the paper out and flip it around for the 2nd slit).
then they used the paper snips to cut the slits out. i like the idea of the 1/2" to do this though.
i know it sounds complicated, but we really didn't experience any difficulty with the customers. they understood and were easily able to do this.
other tips? make sure if you are using the new dimensionals (now the packages only come in the 1/16" width) that you have them double them up - one on top of the other. otherwise there is not enough clearance for the image to actually spin.
another tip - make sure they do not put the dimensionals too close to the slit or the spinning part will get hung up on them.
hope that helps!!!!