Cardboard box, line it/seal inside with styrofoam sheets (makes it a cooler) place in bags with a little water for each(some corals require more/some less) , overnight it, if you google there are much better explanations
+1... Also if the frag is on a plug I usually stick the frag in a small piece of styrofoam and have it float upside down in the bag..that way it won't get damaged.