The sequence of photos is of cutting out the components for an inset hatch. This is not a simple process and definitely adds time to the project. Each hull will have four of these. I cut the straight edges of the opening with a panel saw and then finished up the corners with a jigsaw. You need to work carefully as you need both sides of the cut. Once they are cut out I use a laminate trimmer with a quarter round bit to rond off the edges. Working this way will give you a hatch without wasting material as you use the cutout for the hatch and scraps to make the doublers and the hatch resting lip. You need to make doublers for the catch, the latch and the latch receiver. Once assembled you will have a locking hatch.

Wharrams hatches will do fine. They are simple to build. What I don't like is that you miss the opportunity to make each bunk board a continuous web in each hull section that provides additional horizontal stiffness to the hull.