The top of the lazarette I decided to make out of a doubled piece of 9mm plywood. This makes the lazarette thick enough to match the thickness of the butt hinges I chose, as well as making it plenty beefy to stand up to an anchor and chain bouncing around inside of it trying to get out.
I had to wait until now to finish the lazarette top because the motor mount needed to be completely installed first - that butted all the way down to the top edge of the aft cleat the lazarette would rest on, and once the motor mount was finished I could extend that with a firring strip all the way across the cleat so that the top of the lazarette oculd be a uniform width.
Once the dimensions were worked out, I needed to pull out my handy router template and again route notches in for the hinges, this time on the lid of the lazarette itself.