frugalreefer is right - just slice them at the base. If you put the frags in a tupperware (to avoid current and getting knocked around by crabs and snails) with some small chunks of live rock, they will attach quickly.
They are pretty resilient. I once had one attached to a small rock sitting on a large rock. It attached half to the large rock while still half attached to the small rock. The small rock got knocked off and the ricordia stretched to about 4 inches long. I cut it in half and after a few days I had a healthy ricordia on the small rock and one on the large rock.