Heads are round but a beard can have corners. If you think this passage means that the Earth is flat and square, you also have to make the case that human heads are square. Good luck with that.
Extremity, extreme part, corner: כַּנְפ֥וֹת – kanaph
The Nuance of the Earth’s Corners
Here's a little nuance for you: Human head don't have corners, but a beard can. We can illustrate this by putting a cheese slice on a kid's ball. The cheese has corners, the ball isn't flat.
The Sons of Noah
The time between Noah's flood and Peleg's tectonics was when the dispersal from Babel took place. From Babel small family groups spread out, figuratively speaking, to the ends of the Earth.