The sides of the box are 1x3 clear pine. I have learned to build the box about 1/2" larger than the license plate s that when you are playing it your hand doesn't rest on the metal edge of the plate, it's too uncomfortable.
The neck is an oak 1x2. Its fretted on a 25" scale. In order to accommodate the resonator the neck is cut down before going fully through the box and it is terminated with an oak 1x2 cross member. Seems to be plenty strong enough on my last build, and I've seen others here do the same.
The bottom of the box was hogged our with a dremel to make room for the output jack and volume knob, and the back of the box was made from a scrap of mahogany door skin I was given by a friend.
So far, so good.