$25 Box Dulcimer For First Time Builders
Here's a link to an article written by Dave-M from Phoenix, AZ several years back. He gives clear instructions on making a box type dulcimer using hardware store materials and 1/4" thick "craft wood" from Lowe's or Home Depot. One very nice thing is that he includes a fret spacing table for three common VSLs.
This is a well written intro to dulcimer building in general and replica TMBs in particular.