This article and corresponding video discuss how to do the spinning back kick, a kick that appears to be much more difficult and complicated than it truly is. Without going into the actual meat-and-potatoes of the maneuver, a way to simplify it is to realize that its title is a bit of a misnomer: this kick does not involve any spinning at all, but rather it involves turning. And the foot lands in the manner of a sidekick much more so than it does the sort of toes-pointed-down mule kick that most people would think of when they hear the term “back kick”.
The Spinning Back Kick is a mid-to-long range kick that lands with the sole of the foot-
Turn on the ball of the front foot (note that I used the term “turn” and not “spin”, you are not spinning 360 degrees) while attempting to look over your shoulder at the target. Lift your kicking leg up, “chambering” it. Once you see the target over your shoulder, kick and land with the flat of the foot, following through and pushing “through” the target. The higher you chamber your leg, the higher you kick, as one would asssume. You want to finish with the front foot being flat on the ground, not completing the 360 degree spin.
The kicking foot lands sideways on the ball of the foot or the heel, in the manner of a sidekick. As stated above, it does not land with the toes pointed down as in a mule kick.