Find places where the rock "naturally" fits together (with multiple points of contact) and looks appealing to your eye. glue the points of contact with Gorilla brand Superglue gel and let dry, apply second coat of superglue over the points of contact and let dry, use 2 part epoxy (purple obviously) to completely encircle all contact points. Make sure to use some sort of tool to really cram the epoxy in the hard to reach places!!!