Flat earth claims have exploded on the Internet. However, essentially nobody in Christianity ever taught this, although they had a very high view of Scripture. The Bible simply doesn’t teach that the earth is flat. E.g., the Venerable Bede in the 8th century taught a spherical earth, and Thomas Aquinas in the 13th century thought that a globe earth was one of the most obvious and well known facts of his day. Medieval students could do a better job of proving a global earth than most students today.