There is no evidence that the bible talks about "flat" earth (and all the ridiculous pictures of it, like a flat disc floating in space); so we shouldn't conclude something it does not positively affirm. However, it certainly contradicts our modern understanding of it. So all we know is that according to the bible and it's non-metaphorical descriptions of the creation of the world (which Genesis 1 is without a doubt) there are waters above the sky, and daylight is not effect of the sun. There is no evidence in the bible for space, planets etc., that's all modern secular science/philosophy, foreign to biblical revelation.
So if you try to prove that the bible confirms modern science, or that the bible affirms the flat-disc-floating-in-space reality, you put yourself into a lot of trouble. Let's stick to clear revelation and not get trapped. Both modern science and the flat earth idea are secular.