OPTIONAL - STEP FIVE: You can give your box the look of dovetail joints using the darker colored stain. Using the little brush, paint alternating checkerboard-style rectangles along the vertical edges of all four corners.
I drew a light pencil guideline to make sure that my rectangles ended up the same length. But I didn't measure the space between rectangles, choosing instead just to "eyeball" them. Remember, imperfections merely add to the handhewn look.
Another decorative option is to darken and round the corners of flat panels on the sides of your box (as shown). This helps antique your piece.