I took an old guitar that I couldn't save, removed the back and made shelves from the residual material, and the inner structural wood of the guitar. The only two materials are one guitar and carpenter's glue; that's it! There is a tutorial (link), but it's in Hebrew. You can look at the picture, though... written for Bayadaim website - a Hebrew eco-DIY site.
The Last Acord of the Spices Guitar