How do you do a crossover when jumping rope?

I've been skipping / jumping rope for a few weeks now as part of my fitness routine. I've been trying to do the crossover thing with my hands (boxer style) but just can't pull it off. Can't find anything on Youtube that tells you how to actually do it (there's plenty of skipping videos where people do it but they don't offer advice on HOW). Appreciate it's difficult to describe this sort of thing in words but any tips?