Is it difficult? No, some basic skills are an advantage though.
Does it take time? Yes, like with many good things patience and endurance are required.
Building kits are available from many sources. A kit of frames is certainly a big time saver. You will still need to widen the gluing surface on each frame by gluing balsa sticks around the edges, if you want to guard against delamination of the skin from the frames.
The skin is made up from strips of wood of widths determined by deck camber and preferences for color and pattern. The strips are glued with polyurethane glue and pulled together by stretched household plastic wrap. Works great.
There is nothing like cruising along the shore on your self-made paddle board!