Depends on what you call scratch. And how hooked up you are with machinery. Are you resawing a board? Batch building takes longer, but less time per instrument. Not trying to dodge the question, just trying to say that it depends on lots of stuff, including experience. Call it two days, not counting finishing. I've also had mostly finished instruments sit around for years after losing interest. If I know there's a sale at the end it goes much faster. If I only built for myself I could crank them right out. A day job and age can really get in the way. If you have the drive to kick on through despite all the obstacles you should cherish it, whatever your degree of experience.