If you want perfect placement, I suggest you use the florist clay. But I found that the rubber bands worked very well and held the canes in place until I had the vase totally surrounded.
You can see from a top view how the canes surround the vase.
See how tall the canes are - this is why you have to extend the foam above the lip of the glass vase.
Here's a view from the front side after all the candy canes are in place.