Seeling the Inside and Tracing the top

We just got finished sealing the inside of the boat. We seeled it with oil based primer. We painted the whole inside of the boat with the primer. It acts like a water sealent so that way no water gets inside.
Now we are in the process of tracing the top of the boat. That's the easy part. Put a large piece of luan plywood across the top of the boat and trace it. Then you would cut it out and then glue it and even use nails to make sure that it is sturdy.