palys and soanthid (my "sideways N" doesnt work) colonies actually form new polyps, not split like many LPS, that form at the outskirts of the colony. Sometimes they will kind of "drip" or drop off a colony that is on a wall, fully seperating and hopefully attaching where it lands, and sometimes even will stay connected to the mother colony via long term of basal tissue.
If some have fully seperated, use a gel superglue like Loc-tite Gel superglue. (must be cyanoacrylate) and attach the polyp to a rock or plug. Usually, applying a little glue (about the sise of a pencil eraser should be enough) to a rock, let it cure for 5 - 10 seconds, then using a set of tweesers, apply the polyp (base down) to the glue, let it cure for a minute (additions of saltwater dripping over the polyp can help cure the glue a bit faster)
you can youtube how others do it, which is nice to see.
Good luck.
have fun