Hope I remembered enough to be useful. The rest is up to you and your imagination.
This is my first attempt at Instructables. I have been learning to build mountain dulcimers and stick dulcimers for a few months. This is not really a beginner project. It requires some previous experience.
I took only a few photos during this project, but for those who believe, as I do, that "A picture is worth a thousand words.".... I think there is enough information here to inspire new approaches to building a stringed instrument.
This instrument had good volume and sounded pretty decent to my untrained ears.
You will notice the irregular spacing of the frets. I used a diatonic scale, as is used on dulcimers. Here is a link which offers more detail on the subject: http://www.cpmusic.com/roadmap.html
Some tools you may need: I used a band saw to cut the stick and fingerboard to size. Sanders for shaping and smoothing. Drill press for cutting holes for tuners and the sound holes. A mat knife and jeweler's saw for opening the ends of the box where the stick must pass through, also to cut the fret slots. A screwdriver to secure the tuners.
For materials: I bought a set of three dulcimer strings (12, 12, and 20), the old cigar box, three tuners and the brass nails. The stick, I found out in the desert. It was well aged by the sun and stressed by termites by the time I found it. I used a scrap if 1-1/2" x 1/4" cherry for the finger board and tail piece.
As a walking stick I left space above the tuners for a comfortable handle. The tuner holes (5/8"dia) were below this and spaced about an inch apart . I used 1/4" bit to drill out the holes for the tuning pins to slip in from the side of the stick.
Before moving on to positioning of the stick, cut the sound holes. I used the drill press for mine. The sound holes, it seems, can take any size or shape. I liked this pattern.
The real challenge working with a crooked old stick is to find one side of it that is nearly straight. You must be able to secure the stick where it runs through the box so that when the fingerboard is attached (1)you have a surface perpendicular to the top edge of the box and (2) parallel to the face of the cigar box. You must be able to run a line straight down the center of the fingerboard to the center of the base of the instrument.
To do this requires positioning all the wood parts so they are aligned properly, taping and marking to know where to cut out the box ends. This is intuitive, I just do what makes since with the stick I have to make things fit.