I've done three of these, a six string, a twelve string, and a bass. These photos are the bass. I had a neck for the twelve string, but I made the necks for the six string and bass. You just have to build the box with the structural capacity to attach the neck. These are all bolt-on necks similar to Fender.
Here's the pieces of the box. For some acoustic sound, I'd go larger on the box and thinner on the top and back, and probably a little deeper also.
Here's the way those pieces fit together. You cab see the "tounge" where the neck bolts on, and how it's secured to the box.
Here's the finished bass, from the back. You can see where the screws go through the tounge and into the neck.
