When I was a technician, few things bothered me more than trying to pour a cast with stockinette that was dangling. Many times a cut strip is placed on top of the stockinette which prevents the adherence of the casting material to the stockinette. I would try to use 3M spray adhesive and other methods to keep the stockinette from becoming part of the poured mold.
If a part of the stockinette got into the mold, stripping the material off the cast became a chore. I would sometimes have to cut the stockinette and leave some of it in the cast and then take a torch to burn it so the cast could be modified. All this extra work could be avoided if a clinician would have put the cut strip under the stockinette.