I think making molds with hatch flanges is a waste of time for most applications. It takes a lot of effort to make it come out right and the results are never perfect. The layup is also complicated by having to add fillets around the flange.

Anyone who’s ever built a Brian Laird kit however, knows how to make an absolutely perfect hatch. The fuse comes molded in one piece and you cut the hatch out where you want it with a razor saw. You put strips of tape on the back so resin won’t stick, and then tape it back in place while you lay up a couple of layers of cloth behind it. When the resin cures you pop the hatch off and cut out the opening leaving a flange of about 1/4" around the perimeter. The hatch now fits absolutely seamlessly. And you didn’t even have to go to the extra effort of making a separate hatch mold!