You can attach a fresh fragged leather a couple of ways one is putting in an area with low flow and a bunch of rubble, loosely rubber band it to a piece of rubble, take a needle and thread and run the thread through it the stock and tie it to the rubble, and the last I know of is to take a tooth pick and run it through the stock and then use a rubber band to hold it on each end of the toothpick looping it around the rock.
When you frag your leather it is best to take it out of the tank so when it releases it slime it doesn't get on other corals and irritate or kill them.
That is a finger leather I have one that needs to be fragged it is the size of a soccer ball when fully extended.