Actually, what I've read about the "circle of the earth" in Isaiah 40:22 is that chug does mean a circle. Looking at the word's entry on BibleHub, you can see that the concordances give the definitions "circle", "horizon", and "vault". It would be nice if there were more usages from which to get a sense of the word, but there's only three. As you can see, the second is in Prov. 8:27: "when he inscribed a circle on the face of the deep". Both the Isaiah and Proverbs verses would make sense if referring to an Earth that is flat and round.
The other usage is in Job 22:14, where it refers to God walking on the vaulted ceiling of the sky. This complicates the definition a bit and I'm not clear on why chug can mean both "circle" and "vault". Perhaps the three-dimensional nature of a vaulted ceiling is why some claim that chug can mean circle, but all it tells us is that God is dwelling above some kind of round structure, which could also refer to the firmament as a sort of hemisphere.
If you look at the page I linked to on Contradictions in the Bible, there's illustrations (approximate ones) which show a literal interpretation of the Bible's word-picture. Part of that word-picture is given in Genesis 1 when God hammered out an inverted bowl shape (raqia, the firmament) in order to create a space for life in the formless waste. The reasoning for calling the raqia a bowl shape is given in footnote #1 in the Contradictions article. You can see the same definition of raqia if you look at the Brown-Driver-Briggs entry for the word on BibleHub.
As for the scripture about hanging the earth upon nothing, the verse takes on a different sense if you focus on the word "hanging" rather than "nothing". The writer is not necessarily saying that the earth is in the middle of an empty place like outer space; he is simply saying that it's not hung from anything. That's because the Bible speaks of the earth resting on foundations (Prov. 8:29). Contributing to the idea of a flat earth (more accurately, a flat land) are scriptures like Isaiah 41:5, 9 which refer to the "extremities" of the earth (a sphere has no extremities, right?).
The fundamentalist argument is that this sort of phrasing is poetic language, and certainly that's what I believed as a Witness. It was a striking thing when I first contemplated that these verses might have been meant literally at the time they were written (similar to how the Bible refers to the heart as a place where thoughts occur, which is taken poetically now but was meant literally at the time).
This post may not be as coherent as I would like because of my tiredness, but hopefully you get what I'm trying to say.
