I skrt of did this after watching the HORRID Gods of Egypt movie. Ugh. But it did get me thinking. And here's how I did it.

The world is a flat disc floating through space. The sun and moon are literally vehicles (though none known to mortals) that the gods use. Stars are... A complicated mix of things. The other side has a giant maze that acts as the land of ghosts, demons, and undead, that leads to the center where the judges sit and jidge people if they are worthy of passing to the afterlife.

The between are caves. People have been known to dig deep for gold and valuables, but also to assure a way to the center so that their souls have a way there. It... Usually doesn't work and is a bad idea, since either you have to create a maze, or demons come pouring out. Also, since halfway down gravjty switches. So you go from being pulled down to being pulled down in the other direction. And there are giant caverns in the center belt where, if you are unlucky and fall without restraints, you'll just float there. So there's no "center" per say, rather a belt where gravity changes (about 10 feet long just so I could mess with the players). Also if you fly too high you just detach. From the highest mointain you need to jump a bit higher than your average mortal and you're home free. For about 5 minutes before the vacuum of space kills you since you can't breath.

Next are waters. How do they work? Well, there are rivers that flow off the edge. Usually they would just float off into space, but there is a goddess responsible for capturing them into jugs and passing them to another that pours them back into the rivers. There are rivers that end up in lakes or go underground, or evaporate and come down as rain. But there are no oceans. You could have oceans, depending on how the gravity works (do the sides of the disc pull tiwards themselves as well?), or if the ocean is in the middle surrounded by land. In which case I'd say have the disc be larger, with the outside continent, one or two more inside continents, and a dozen islands. Or just the outside with islands in the middle. Note that you can at all times, see hazy things in the distance of what everyone else is doing. So secrecy is hard, but not impossible.

Anyways. That's how I did it. Hope that helps.