Get a piece of wood, 1.75" x .75" x 2'.

Call this the "neck". I used poplar, next time I won't. You might be better off with a hardwood like oak or maple. You can get poplar or oak at any big-box hardware store. It's really cheap. Poplar cuts like butter, which is great if you're using hand tools.
Get some more wood, 1.75" x .25", build a box. For the back, use a .25" x 5.5" (?) board - I forget the exact dimensions of these boards - but they're the thin and wide boards, obviously. Cut the back first and use it as a template to build the sides. Don't attach the back yet though.

Make some cut-aways on the ends, roughly .5" deep x 1.75" wide. The neck is going to fit into these.


