Couple of hints from the fibreglass point. While the router is out knock all external corners to a small radius. And all internal corners mix up a brew of polyester resin and talc powder ( cheap baby powder is good) into a thick paste that won't sag off a putty knife. now feed it into all the internal corners. Use an old desert spoon to make it a smooth radius. Now lay up the resin and chop strand Matt onto wet bog mix. Fold glass up and over the top lip of box.
Quick sand for daggy bits then flowcoat. Speckle Finnish if you like and job done.
Might be worth adding a drain tube out the back into your motor well if you want to get rid of the blood.
Handles to lift out of boat for cleaning?
Otherwise have fun with it and don't mix your resin too hot.