When you reach the edge of the world, it's not clear that it's actually an edge. Particularly on the cloth map, iit should be possible too draw a neat line with some things beyond that aren't the sea but a void, so we can see clearly that we reached the border.
I think of a Discworld-like border of the world, with water pouring down the edge on the 3D map, and some drawings of stars in the distance on the cloth map.
