Fred,
Bare in mind that I have only made two of these myself but I can tell you what I have done...
I take the blank and cross cut the top and bottom so that it is flat. This just removes the uneven angled pieces that get cut off anyway on the top and bottom. Once flat, you will see the intersection of the 6 pieces. I then mount the blank between centers at these two points and turn the blank round. Once round, I mount in my collet chuck and drill down the center.
Hopefully someone that has done more than me can help out. I know the time it takes to put together one of these blanks. I would hate for it to get ruined at this point. BTW, your blank looks awesome! You did a good job so far from what I can see with tighness of the joints!
Good luck!
Fred