Recently completed my first 3 string (not exactly a cigar box)  The curved sections form a rectangular frame made from a scrap wooden chair, a piece of ply board from a 1950's is screwed to the back of the body which also anchors a section of timber to which the neck is screwed onto. The guitar neck was fashioned from a scrapped fender style strat copy together with the bridge and pickups. The hardest challenge was narrowing the neck. The resulting tone is very pleasant and typically electric. The small matching amp I built from a left over pair of computer active speakers, these were popular way back when computer towers dominated. I modified the front end with a mosfet preamp circuit to take the guitar but also added a switched line input. The output is around 10 watts and is powered by a 12 volt external AC power supply.