Have you ever seen something approach from a long way away? Did you notice that you don’t see the whole thing at once, you see the top first? If the earth were flat this would not be the case. Also a flat earth could not have the very useful magnetic poles that function the way they do on our earth, the night and cycle would work completely differently, and gravity would be tricky.
The earth has never seemed flat to me. Just look up in the sky, it is clearly a dome over a round object.