Post #19, 5/12/2021 of this thread shows some of the details of the neck joint. Keep in mind that the string tension on a tenor ukulele is 40#, compared to 150#+ on a steel string guitar. Thus I am not using any kind of post, just two 1/4”x 3” Allen head cap screws. The neck block is elongated and because the top and back are arched, two additional pieces of wood are glued to the top and back of the neck block. The top piece supplies the mating surface for the neck, and is cut parallel to the sides. The appropriate size slots are cut into the top and back when assembled. The leading edge of the top piece protrudes slightly above the top, while the back piece is sanded to match the shape of the back. With this design there is no need for a neck heel, allowing greater access to the higher frets, and making up for some of the extra mass of the neck block.
Brad