OK, I partially misunderstood. If I were building with strips, yea I agree with what you did. I guess you could build around a form but that would be a lot of work seems to me. Building from plywood, it's simple to do around the form than try to make if fit inside the boat. I tried and saw really quick that wasn't going to get it.

Marking it for trimming was easy. Easier than I expected. Once I got it level and anchored onto the deck it was simple to make and cut. Now I wouldn't wanted to trim that without my bench! That would be hard.