Dougie, they do have answers for those questions (the answers are wrong, but they have them, and the wrongness is sometimes pretty subtle).
Job doesn’t say about the shape of the Earth, though it does say that it’s finite and it’s not resting on top of anything. Isaiah indicates that it’s round, but “round” and “flat” are not mutually exclusive (look at a manhole cover). I suspect that Jewish or Christian Flat Earthers cite these same passages as evidence that THEY’RE right.
In some cases, they’ve even done experiments. I recall several years ago reading about some measurements they made in a very straight section of a canalway involving a telescope and a large disk. It was possible to see the disk at greater distances away than you’d have expected based upon geometry and the “alleged” curvature of the Earth, which they concluded proved the Earth wasn’t actually curved (in fact, their experiment indicated that if it WAS curved, it was concave).
It turns out that refraction of light in the air over the water in the canal can explain this just as well as the Earth being flat (or concave), but that’s much more difficult to understand or explain than “The Earth is flat. It looks flat, it IS flat; the experiment proved it.”
Also, as mentioned before the Earth can be flat and still round, so the shape of the shadow on the moon doesn’t contradict a flat Earth even if you accept that it’s Earth’s shadow (which I’m not sure they do).
And other posters are right about them APPEARING to take themselves seriously. The application forms I’ve seen have a clause in them which goes something like “I hereby swear or affirm that I am not joining the society to mock or discredit it.”