OK, I'll try again.
Think of the Earth as a being, a massive being under our feet (Great A'tuin comes to mind, but that's a complete different matter).
As a being, it has an spirit that more or less fits its shape. Vast, round and, from our point of view, flat.
Now think of the Hover Boots as a mean to achieve physical contact with spirits: some gloves made from the same material would enable you to
touch ghosts. So the Boots allow Link to step on spirits, which isn't really useful unless you want to kick Poes to death... But then again, Earth's spirit on which Link now walks (and that gives the sensation to be walking over something slippery), is
not exactly the same shape of Earth itself, but slightly bigger -spirits usually are, that's why they glow. So now Link can walk a few steps beyond the edge of land,
because he's still on Earth's spirit.
Wow! Thank you very much, you made me put my confusing ideas in order. I hope now is much more clear than before!