Cut approx. 13" of your chosen flat leather cord (or the amount that comfortable wraps around your wrist twice.)

Pierce two 1mm holes at each end of the leather. This will be where the clasp and extension chains are attached (see image). 

Attach a jumpring to each of the holes. Add two lobster clasps to one end of the leather. Add two extension chains to the other end of the leather.

Using strong cutters, cut off any loops from your druzy pendant or connector. 

Measure approx. 3.5" from your lobster clasps on the leather cord.
Add some drops of glue and glue on the flat side of the druzy crystal.
Leave to dry.