Hmm. I haven't read that you have to router the edges before. I figured it I couldn't get a water tight seam with Weld-On #4, I could just run a thick line of Weld-On #16 down the seams and it would hold. Then again, I've never done this before so i really have no idea. I figured with such a small container, it wouldn't be that big of a deal. Maybe I'm wrong though.