I have a wonderful "cake box" that I use for sheet cakes, and other flat cakes. It is a rectangular storage box (Rubbermade-type, but I think a different brand). It is about 12"x18" (approx). I can put an 11"x17" cake on a cardboard meant for cake on the lid, then put the box over it and snap into place. (So basically, I am just using the box upside down). I love it! I've used it for about 9 years, and do so many more rectangular cakes than I did before I had that box.