I built a kayak, a Pygmy Osprey Standard. Unlike people who are diligent, it took me a long time, and I learned all sorts of problems with working with epoxy, and some of the solutions.
It's built from a kit, using a technique called "stitch and glue". The kit came with all the materials, including pre-cut mahogany marine plywood for the shell. The edges of the frame are stitched together with wire stitches, then glued. The stitches are removed, and the boat is fiberglassed inside and out.
I finished construction in late 1999, painting and varnishing it in 2001, and have successfully taken it out in the ocean without sinking.