Bible theory or rampant imagination? They were not talking of the universe but of the Earth that it is flat. As for the shape of universe, we do not know. In 'Manifold' (many dimensions), it can have any shape. Hindus saw it as an egg, Brahmanda (anda being egg).
Manifold - Wikipedia,
manifolds - Google Search:
Bible theory as based by creation scientists. Let me address this in more detail. The Earth is described as a circle in the Bible, but it is not flat. From high above, it looks like a circle but isn't flat. It could be spherical.
“I saw four angels standing at the four corners of the earth, holding back the four winds of the earth." Revelation 7:1
John is using an idiom in describing people coming from all parts of the world. The Book of Revelation (prophecies; describing the future) uses non-literal and symbolic language.
"He stretches out the north over the void
and hangs the earth on nothing." Job 26:7
"He sits enthroned above the circle of the earth,
and its people are like grasshoppers.
He stretches out the heavens like a canopy,
and spreads them out like a tent to live in." Isaiah 40:22
This alludes the Earth is spherical, but not definitive. The Bible does not teach a flat Earth, but doesn't teach a spherical one either, but describes it.
The shape of the universe is flat. It is described in the Bible as that of a canopy like tent that is stretched out in all directions.
Since we discovered the CMB, we see the universe as such in this 4-D model. If you look at the ends, then you can see the universe is flat.
I think the secular or atheist scientists are going to state that the universe is circular, but the Bible describes that of a canopy like tent and that like a scroll which curves at the edges (middle). What do you think?