So the unshaped neck gets attached to the underside of the structure. The screws will attach to the neck where the truss rod channel will be routed out after the fact.
It's off centered because the mitre slots on the table saw are not an equal distance from the dado blade on each side. I still have to add the sides of the unit to what you see here . These sides will be what slides in the mitre slots. Well I was just about to go and add the sides but my wife just brought me a huge bowl of ice cream. And The big bang theroy is on in 20 mins......Oh well, tomorrow?