You can cut leathers like you would a branch off of a tree.
Super Glue GEL is supposed to be great, but I have not had much luck with it, and I have been fragging/attaching coral all week.
If your substrate is deep enough, the a more natural way is to put the frag in between 2 pieces of LR, bury the base into the substrate, and in 2 weeks or so it will have attached.
The other thing which works (and is MOST natural) is snipping off a frag and let it float around until it attaches where it wants. I did this 2x this week (accidentally), and I have a xenia frag and a sinularia frag growing well in strange places!!! The xenia attached itself under a piece of LR and I couldn't see it until it's little polyps started squeezing out from under the rock. That was VERY cool, cause I thought I had lost the coral.
Good luck, it's hards to mess this up!