Use a scalpel, or xacto knife. Reef rock is usually fairly soft. Brush your fingers, where nonpowdered surgical gloves in case you are senestive to the critters, to close it up some. Then use the blade to dig a small pc. of the rock where the base is attached. You should be able to remove just enough so the ric stays attached and leave you something to put super glue gel on and reattach where you want it.
If you can't get the rock cut the base of the ric as close to the rock as you possibly can get. Then put it in a small tupperware, clean of course, container with some rock rubble and sand or crused coral. Take a pc. of netting and rubberband it over the container and place it in the tank. In about a week it should attach to something that will allow you to glue it where you want it. This method may leave some of the ric behind on the original rock and it may just grow a new one there.
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