When attempting a Superslide or a Megaflip, you can sometimes accidentally cause what is known as a Weirdslide.
A Weirdslide can be anything from Link glitching into the ground to Link sliding back and forth rapidly. If you extend the slide into the air you can walk sideways and you will hover in the other direction. This is an example of the superslide's negative speed.
It is worth noting that although it only lasts for about 3 seconds, a Weirdslide can give Link a high speed without being stuck in an animation like Superslide and Extended Superslide, so he can walk around and use items during the slide.
This works on anything you could megaflip off of. Works with Nayru's Love, too.
Experiment with many things like stick angles and how many times you tap the stick back. Try doing it sideways too.