I think in their crazy world, the north pole is at the center of the earth disk and Antarctica is actually an ice wall around the perimeter that keeps the water on the disk. Therefore, Africa and Australia are on opposite sides of the disk (like left-right not heads-tails) or are near the out perimeter and no one would build a cable going across that long of a distance.

If that makes your brain hurt because of the stupidity, that's because it is. Flat earthers are only good as the target of a joke because we can all agree that it's stupid. There are some entertaining videos on YouTube of people making fun of them, or of themselves proving themselves wrong.