The earth is round like sphere formed, a ball this we know.
A flat earth is not what is generally meant by some, like some kind of flying carpet.
However, it is not to be taken so but a deeper explanation is required, it is written in the Tanya that certain things are imossible to explain in writing.
For what it is worth, it is possibly describing a scroll, which is round when rolled up, but can be rolled out flat.
For if one sets out on a journey with the help of a compass, and keeps going due West, 270, one will come back to where one started.
Unlike if one sets off due North, there is a hinder, a pole as in Npole.
To continue one would have to change course from N to South, where there is another pole.
If seen as for example a Torah scroll, with a handle at top and bottom, so as to be able to roll out flat.
Just my way of trying to make sense of the claim of flat earth.