Maybe four corners of the earth or four winds is a reference to north, south, east, and west or quadrants on the Earth. Wind doesn't have a corner so it stands to reason, at least in my mind, this is figurative language and not a reference to a literal corner.
Contextually, the four corners, four winds, ends of the Earth is just a way of saying from every direction or from everywhere.
What you really need is a verse that literally says the Earth is flat or spherical. The Bible does not confirm or deny the Earth is flat or spherical.
Ezekiel 37:9
9Then said he unto me, Prophesy unto the wind, prophesy, son of man, and say to the wind, Thus saith the Lord GOD; Come from the four winds, O breath, and breathe upon these slain, that they may live.
Isaiah 43:5-6
5Fearnot: for I am with thee: I will bring thy seed from the east, and gather thee from the west;
6I will say to the north, Give up; and to the south, Keep not back: bring my sons from far, and my daughters from the ends of the earth;
Mark 13:27
27And then shall he send his angels, and shall gather together his elect from the four winds, from the uttermost part of the earth to the uttermost part of heaven.
Revelation 7:1
1And after these things I saw four angels standing on the four corners of the earth, holding the four winds of the earth, that the wind should not blow on the earth, nor on the sea, nor on any tree.