I saw a homemade slide guitar once that was made out a piece of hardwood burl. The guy who made it is a carpenter by trade, and he got a big slab of maple for a custom tabletop & bar job. He told me the homeowner wanted his bar & table to look the same and it was more or less the only option given the size involved. IIRC, he said the lumber cost 1500 bucks alone for a 3'' thick slab, and another 200 for them to saw it down to around 1.5''. After the project was done, he asked his client if he could keep the scraps. No big deal at all for the client. He was real happy with the work.
I wish I had pictures of the guitar, 'cause it looked wild. The whole thing looked like a Steinberger with a single humbucker pup and a Floyd trem. The fretboard looked like it was flat as a pancake and made from a strip of mahogany.