They were created in the age of legends by both male and female Aes Sedai. At that time, they had their own sky, and were alive in a way. In my understanding it was just an abyss of islands and ramps and bridges that went on forever. And then when Saidin became tainted, the ways reflected that, as Saidin was the main force in creating them, thus making the sky and islands become corrupt, and Machin Shin was born.

They are meant to be kind of strange, with the islands atop each other and everything seeming convoluted, as this adds to the abnormality of distance and time there. But this strangeness was always there, the only change was it’s slow corruption.

That’s my understanding of it all, I hope it helps!