The 2 main parts are 6"x 6"x 5/8"pine but I think you could use any scrap. Find and mark the centre on one piece. Using a set of compasses mark out a 5" circle and a 4"circle.. Keep the compasses at 4". Place the compass point anywhere on the 4"circle and mark the circle on both arcs. Move the compass to the first mark anti-clockwise and make 2 more marks then continue all round the circle until you get back to where you started. you should now have 12 centres marked on the 4" circle.
I then nailed both pieces of pine together in the corners and also taped them together. I used a drill press and a forstner bit slightly larger than the tubes set to just cut through the top piece of wood and mark the lower piece with the point. I drilled through the centre of both pieces to take the dowel. I then cut the stacked pieces to the 5"circle on the scroll saw. I drilled half way through the base with a smaller bit. Then just sand and fit up.
Hope this makes sense