For this project, we are making giant mushrooms.  to get a variety of sizes, I've chosen to use a couple different sizes of PVC pipe, cut at various lengths and even some smallre 8 inch concrete tubes.

 

We started by screwing these into some 1 foot square OSB panels

 

and then adding joint compound to the bases to give strength and to hide the hardware.

the next steps will be using roasting pans from the dollar store to make the mushroom heads, then paper macheing over those, covering them in joint compound and finally painting them.