You can fletch them the same way that you fletch any other vane or feather. Just because they are shorter does not mean that you can't use a helical clamp.

Don't take this the wrong way but this question is like a person asking that since a 4" vane is so short can they use a helical clamp like they did with their old 5" vanes.

The clamp does not change and the arrow does not change so you could fletch a half inch vane with a helical clamp if you wanted to. It just wouldn't appear to wrap the shaft much being so short.