Hi, over on the Building 101 site, Rich Butters asked about plans for a 3-4 string CBG, I could not work out how to address that to him on that page [whatever its called] as there was no Add+ button as I could see so it would have landed away from his posted question. so I will address it to him here.
Hi Rich, when I first started building CBG's, I had no one to ask about the subject at that time, and had no cigar boxes either. However I did know how stringed instruments worked, I knew what was important in their construction and sound output, and the easy part was I knew what a box looked like. I started as an apprentice making boxes, but that's another story.
I don't know how to share these plans, as basic as they are, other than to show you a photo or two. you know what a box looks like, you really just need the dimensions, and some assembly detail.
The size of the box I settled on after making quite a few cbgs was/is 113/4 x 71/4x 21/2" all internal measurements, [complete with plans for each prototype] that's what is shown here.
I made a video some years ago of the building process, its pretty basic beginners stuff, but my son had his first cbg assembled and playable in a Sunday afternoon after viewing it.
This not what you were looking for but best I can do