I used one piece spacers. Just before installation, I laid all the spacers and coaming ring on the workbench upside-down. I then glued eveything together , drilled pilot holes and nailed in tacks (one in the front and one in the rear) that would go through the spacers but not all the way through the coaming ring. Then I installed the whole thing on the deck. This keeps all the parts from moving around while you place your clamps.