[R. Scott]

I believe the “World is Flat” was pretty much relegated to churchmen and people who had never been to sea.
People weren’t stupid. If you are near the ocean stand and look at it from the shore. You will see a noticeable curve to the horizon. Board a boat and head out to sea. First the shoreline will drop below your horizon, than the higher land and finally the hills.
Watch an approaching boat. The first thing you se is the mast, then the hull and finally the waterline.
Head back toward shore. The first thing you see will be the tops of the hills, followed by the lower hills and finally the shoreline.
The only explanation is that you are on a curved surface. The Greek Erastothenes measured the circumference of a spherical Earth over 2,000 years ago

[Jedi Master Pikachu]

The Greeks did have the opinion of an Earth with a circuference--but that idea fell out of mainstream later, and then came back even later than that.

As for the "churchmen" part, do try to lay off of the snide comments about "religious folk," if that was your intent. The geocentric universe was not a Christian theory (it was Ptolemy's--from A.D. Alexandria), and there is mention of the world being round in the Bible.