Curved back dulcimers
Instruments- discuss specific features, luthiers, instrument problems & questions
There are two curved backs of course which can be utilized separately or together. Curve from fore to aft; and curve from side to side. Each by itself is easy enough to incorporate into a design. I've seen dulcimers with 1/8" rise from side to side or head to tail. Several builders incorporate one of these two techniques to help direct the sound upward (to what degree this is successful I don't believe anyone has subjectively proven).
A 'bowl back' is hard to accomplish unless the builder starts with a thicker plank and "carves" the bowl shape into what will become the inside of the instrument. This is done the same way a violin top is carved -- with chisels, rasps and sanding. I don't know anyone who does this for backs-- it is certainly time consuming -- but Ken Bloom does it for the soundboards on his bowed dulcimers, but not, I think on the back.

The "intonation" as you call it is set by the distance from the inside edge of the nut to the face of the bridge. Just don't use epoxy or "super glue" as they are realllly hard to remove if needed. Titebond can be released by an appropriate application of heat.