At the bow was the first challenge of cutting a small square hole for the small beam at the bow. I made sure my chisel was good and sharp and lightly cut the shape, little by little. Too much pressure can chip or split the wood, particularly on the back side of the cut, so this took a lot of care.
With the first hole cut to size, the alignment of the opposite hole was aided by running the beam into place to see where it lined up. It was then cut in the same manner.