how to frag leather finger coral
 

any tips would be nice this thing is getting pretty big

I would remove it from the tank with some water. Cut what you need and rinse it in the removed water then put it back in the tank. Discard the water you used to cut and rinse in. I would also recommend running carbon as a safety measure.

How do you secure it to the disc or rock or whatever its going on? Can you glue it?

A razor blade works best for cutting. Clippers tend to crush the tissue a bit but they work fine too.

Just use a rubber band to secure it. Not too tight as it may cut through but tight enough so that it stays on the disk or rubble that you are trying to mount it to.

Edit: youtube.com has roughly 1000 videos that show up if you do a search on coral fragging and coral propagation. There is also this frag of the month article in reefkeeping about leathers. http://reefkeeping.com/issues/2006-09/fotm/index.php