Swivel/click: The skinny end of the swivelly part goes through the hole, and swivels back wide and clicks into place.
This way would be probably the least fun if you're looking for a do it yourself project.
It seems that before the swivel design became prominent, there was a flexible design with jump rings and cross bars or chain.
These cufflinks feature such a design:
http://www.jewelryexpert.com/catalog...ks-Gallery.htm
The flexibility would be required in order to push the rather large (they seem to be hitting 1/2"+) and flat decoration through the hole.
The findings should be easy to locate and also come in a wide variety of metals, and the process should provide a fair amount of entertainment.
A more bulbous decoration (beads/pearls) I think would require it to be smaller, because it can't be folded back. If you want something larger than can be pushed through the hole, you'd have to do something with clasps or other on/off thing that can be disconnected to push the stem through the hole, and then attached back on the outside of the cuff. This may be too cumbersome, as it requires some one-handed dexterity. If the decoration can be pushed through the holes, a simple curved stem should suffice, but, again, I don't know how much fun that is...