Hit up your dollar store for the following items....or use your own random bits around the house to make it for free.
Turn the glass upside down so the bottom is now the top, add super glue (or epoxy) to the top (what used to be the bottom), center the plate over the glue and secure. Let dry per instructions and there you have it, your very own homemade $3 dollar (or free) cake stand! You can also do this with a white dish, using a white bowl as the bottom. It'll look clean and contemporary. A tip, the taller the glass the smaller the plate should be as you don't want it to topple over. Another tip, if your dollar store has it, use an ice cream dish (instead of a glass) like the one below. It adds some curvature and looks phenom.
Well, that wasn't that short but it sure was sweet.