Backside 1080
The Backside 1080 is a 720 degree spin starting from backside stance and finishing with a hook or outside crescent. It becomes a lot easier if you break down the two spins. You basically just jump up really high while you spin one time and then you just perform a Cheat 720 afterwards on the way down.
01 Backside 720
Even though the Backside 720 is a full 360 degree spin it shouldn't feel like it. It should just feel like a quick turnaround to a hook kick. That's all it takes to do a Backside 1080. Just a 360 spin followed by a quick turnaround.
02 Backside 900
The Backside 900 will teach you the correct hip position to pump over for a 1080. If you have a decent 900 all you need to do is NOT kick but instead you just pump your knee over to land on your round kick leg.
03 Pop 720
This is almost the same trick minus 180 degrees of rotation, because it starts in frontside. However they feel very similar and you can view the Backside 1080 just as if it was a Pop 720 but starting with your back facing the twisting direction.
04 Backside 1080
Enter your backside stance, squat down, wind up and push up hard while spotting the target. Keep your arms open until your chest faces it. Wrap them in and spin around once, while still rising. Spot your target again and then quickly turn around for a hook kick. It should feel like entering a stepover hook or Cheat 720 from midair. That is when the Backside 900 and come in handy. It's basically a Backside 900 that is canceled after the first spin into a stepover hook kick.
Tips
If you have trouble gaining height or staying vertical, try shrugging your shoulders up while you jump.
You can also practice standing Pop 720s to prepare for this trick, however standing frontside tricks always felt very ackward for me personally. See if it works for you.
The spinning technique described in this guide also works very well for Cheat Kicks with multiple rotations.