You want to talk about imagery, terminology, and visions -- how about the imagery used by Holy Scripture, which has a higher trust rating than any prophet or saint?
How many times does Holy Scripture talk about the "four corners" -- and even applies that to other things, no doubt as a reference to "the four corners of the earth"?
Do a DRBO search if you don't believe me. That phrase is used dozens of times.
https://drbo.org/cgi-bin/s?q=the+four+corners&x=0&y=0&b=drl&t=0
Spoiler alert: a ball doesn't have 4 corners.
Another interesting thought experiment: why wouldn't the God-designed altar be a ball (to represent the earth) rather than emphasize having FOUR CORNERS which Scripture also describes the earth as having?
The subject of "four corners in Scripture" is definitely a tick-mark in the PRO column for Flat Earth, that's for sure.
"After these things, I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that they should not blow upon the earth, nor upon the sea, nor on any tree."
-Apocalypse chapter 7
Is it possible that the words God uses have such richness and depth of meaning that they go far beyond our common understanding and accurately describe even complex ideas in simple terms? I was reading Ecclesiasticus recently, and contained in the prologue is "...pardon us for those things wherein we may seem, while we follow the image of wisdom, to come short in the composition of words; for the Hebrew words have not the same force in them when translated into another tongue. And not only these, but the law also itself, and the prophets, and the rest of the books, have no small difference, when they are spoken in their own language."
What is a corner? I think of where 2 lines intersect on a square, or 3 lines in a 3 dimensional room. 4 walls of the earth would not work because that doesn't indicate a complete enclosure as there may be no ceiling, and walls do not restrict movement in any one place since a person can move along the wall one way or the other after having reached it. In a corner, all limits come together, and the only way left to move is back to where you have already been. If you travel around a globe, you will eventually reach the limits of where you have not been, and even by continuing forward, will move toward where you have already been.
Why 4 corners? Shapes exist with more or less than 4 corners. We can move in a theoretically infinite number of directions, but the minimum number of directions to move anywhere on a surface can be reduced to a combination of 4. 3 would almost work, but a vector using more than one direction out of 3 would call for movement in opposite directions, so 4 is the lower limit.