How long has it been sitting? If it doesn't have any roots, it should not be receiving any water.

It's been sitting for a month now. I've watered it about two or three times because I wasn't sure if I should.

I would just give it a bit more time, undisturbed. If it fails, it fails.

Keep it flat on the soil, no water required. Mine usually take much longer than a month to root. The roots will grow out the side, not from the end.

your cutting seem to be very long! Not sure if this would be an issue. Anyhow I would also check that the stem in the dirt is not getting soft and rot. If it fails, I would try to cut closer to the tip of the stem, as long as the stem is still firm/healthy, let it callous for a couple days before placing the cut end in the soil, 1/2 to 3/4 inch deep. And as said by mesembs, no water until rooted.

Alain - For these types (Stapelia, Huernia, and related) the roots emerge from the side of the leaf, not necessarily the end.

They look weird and it's a bit strange, but that's the easiest way. No cutting required just takes time.

That it is a longer leaf is not a problem. =)

Ok, thanks for the clarification :)