There is a verse that says the Lord sits above the circle of the earth . I think most people who used the stars as navigation could probably surmise that the earth was round . The flat earth people i think actually believe the earth is shaped like a American football. I think the average person in times past probably didn't care , they were trying to stay fed.
That video that I watched that max had linked to with some guy trying to explain this stuff ------- so afterwards he did a Q&A with audience and he had up there " flat earth map - basically a rectangle and someone asked so do you just fall off if you sail past the western most edge of map? I swear I think he explained it as " no, I believe once you past this point you kinda just pop right back up here ( now on the eastern most part of map ) lol not kidding!