Step 3: First step: cut the wood
The first step is to cut the wood into the shapes that you need for the box. I won't give exact dimensions or shapes, because you should decide for your self what size you need.. But have a look at the pictures to get a general idea of how I did it, to stoke your rock-n-roll creative powers.. I used a skil-saw (circular blade, hand-held) for most of the cutting.
If you look at the picture of the final box, you can see that the overally shape is two wedges that fit together. Note that the diagonal seam where they meet doesn't have to be a straight line - in fact, making this boundary curved may help the two pieces fit together even better (props to Ben Vigoda for that idea). You could make that seam curvy by cutting the side of the box from a single piece of plywood, and using one side of the cut for each part.