below deck fish box

[Sangster21]

I have a section between stringers about 36 inches long that I can use as below deck fish locker. I am replacing stringers and deck so I have a clean slate to work from. I have done some searching but have not found what I am looking for. I don't see any manufactured hatches big enough so I will need to make it. I think I will build fish box insert so fish guck doesn't end up in the bilge. As such I don't want it to fill up with rain water so I imagine I need to incorporate some kind of gutter underneath the hatch to divert rain water. I am sure there is a "standard" way of going about this.... I just don't know what it is! Any ideas?
Alan