Here is the setup I use for holding a dulcimer on it’s side. I briefly mentioned this clamping method in a recent post about using a spokeshave to bring the top and back flush with the sides. I was scraping the sides of this dulcimer and saw a photo opportunity to show a little more detail about the clamping setup.
I use two cabinetmaker’s clamps clamped to a work-board. By clamping only one jaw of the cabinetmaker’s clamp the other jaw remains adjustable.
Before using this setup I would hold the dulcimer between my knees and under my chin. This method worked well but clamping is a little easier on my body and does hold the dulcimer more solidly.
I occasionally consider making a dedicated fixture for holding dulcimesr on their sides; something along the lines of a Moxon vise, but the cabinetmaker’s clamps work fine and I prefer to have fewer tools with multiple uses than multiple tools with fewer uses.