In the 1960’s Pop Artist Claes Oldenburg began creating sculptures out of non-rigid materials such as cloth, plastic, and foam rubber. Think giant plush hamburger. This became known as soft sculpture and has continued to be popular. Google soft sculpture and you will come up with a myriad of results including how-to instructions for practically any kind of object.
My mushrooms are not as big as Oldenburg’s hamburger but they don’t take up nearly as much space.