Our boat came with a "custom made" hatch prop. A 1"x2"x10" piece of unfinished teak. Inserted longwise it held the hatch wide open, edgewise just a bit open, and laid flat just a crack.
Even though it was "stored" just laid on the after deck outside the hatch, it somehow survived TWO circumnavigations just fine. We had it wash overboard after a year. Bummer.
Great Guana Cay, Bahamas