Take a razorblade, cut them by the base. using tweezers to hold them. this can be done inside a small bowl of tank water.
now you will need some puddy, the stuff we do our rockscaping (aquamend) now make a small disk with a piece, next put some super glue gel on it, attach the zoa to it, let it dry in your bowl of water, then add superglue to the bottom of the disk and attach to rock in tank.