The idea that it is the universal background of the OT that the world was Flat and had a metal dome isn’t universally accepted. Dr. Vern Poythress in his book (P. 96) “Redeeming Science” gave his thoughts on this issue:

8 Sometimes it is said that the language in the Bible arises against the background of ancient “cosmology” that postulated underlying waters, then solid earth, then a solid “firmament” dome for the sky, then the sea above the firmament (Paul H. Seely, “The Firmament and the Water Above. Part I: The Meaning of raqia‘ in Gen 1:6-8,” Westminster Theological Journal 53 [1991]: 227-240; Seely, “The Firmament and the Water Above. Part II: The Meaning of ‘The Water Above the Firmament’ in Gen 1:6-8,” Westminster Theological Journal 54/1 [1992]: 31-46; Seely, “The Geographical Meaning of ‘Earth’ and ‘Seas’ in Genesis 1:10,” Westminster Theological Journal 59 [1997]: 231-255; Seely, “Noah’s Flood: Its Date, Extent, and Divine Accommodation,” Westminster Theological Journal 66 [2004]: 291-311).

For one thing, the ancient Near East did not have one unified “ancient cosmology” but several accounts—Sumerian, Babylonian, Egyptian, and Hittite—contradicting one another at points but nevertheless with some similarities. Genesis 1, as we have observed, does show some similarities to these accounts, but it repudiates the pagan accounts in favor of a monotheistic alternative.

Now, for the sake of argument, let us suppose that from these mixed pagan accounts we can distill a core of assumptions that were also shared by ancient Hebrews. The Bible nevertheless describes things that Hebrews (and eventually other readers) could see for themselves. To suppose that the text teaches detailed technical cosmological views is to confuse the text with the totality of what its readers may have believed. Moreover, a modern cosmological interpretation of the ancient accounts may sometimes impose on the texts a preoccupation with physicalism that does not belong to this kind of literature within the ancient cultural milieu. For example, the idea that the firmament is literally solid is disconfirmed by the statement in Genesis 1:17 that God set the lights “in the expanse [firmament] of the heavens.” If the lights in heaven were literally embedded in a solid, they could not move in the way that they obviously do. Perhaps some ancient people could see the obvious, as well as be skeptical about alleged physicalistic implications of pagan cosmogonic stories.