Floral designers are using just about anything as a container these days. If you'd like to play, too, just look around the house, thinking "shape."
Definition: A boxy container, with or without a lid.
We used: A cardboard lunchbox from a craft store. To make it watertight, insert plastic containers or line with floral foil (foil backed with plastic, available at florists' supply shops.) Floral foam holds the flowers in place.