In the beginning God created the heaven and the earth. (Gen 1:1)
This is the opening statement of the Bible, the very definition of the word: universe (the single spoken sentence). It is a proclamation of the first three things that God created. He created the beginning, that is time. He created the heaven, notice that it is explicitly singular. And He created the earth, which He goes on to describe in the very next verse.
And the earth was without form, and void; and darkness was upon the face of the deep.
At this point on the first day, what does the earth look like? How could it be without form? It must have its own form, but no other form. Does this mean that it must be uniform? Which of the following two are uniform?
The flat earth model cannot be uniform unless it is infinite, that is, it goes on forever! But not even the Flat Earthers are claiming this. And it cannot be just flat because in reality only three dimensional objects can exist in our universe, so really we are looking at a type of platter earth model because it must have depth and circumference. Therefore the flat earth model is composed of at least three forms: flat, a 90 degree angle or curvature to form the edge and the curvature around the circumference, which cannot be equal to the first curvature, otherwise it could only form a perfect sphere. The geometric shape with least surface area to mass is a sphere. Matter itself, especially liquids tend to get spherical to minimize their surface area. In conformity to this fact, a Spherical Earth would be the natural formation created by God. Only a perfect sphere can be without form and void. We also notice that the earth was covered with water, only described as deep.
And the Spirit of God moved upon the face of the waters. (Gen 1:2)
Before God’s Spirit moved upon the face of the waters, there was nothing but this perfect formless and voidless sphere called the earth as the central focus in an infinite and otherwise empty time/space continuum called the heaven which you couldn’t even see if you were there, because there was no light. Notice that there are no defined boundaries to the heaven that God created on the first day, only an infinite universe is described here, with the Flat Earth model the description is incomplete.
The heavens declare the glory of God; and the firmament sheweth his handywork. (Psa 19:1)