The most important thing when doing the fakie backside flip is foot placement. You want to have your back foot in the middle of the concave, and have your toes hanging off a bit. Your front foot should be in the Kickflip position, maybe a little more down or up, whichever feels the most comfortable.
When you're about to spring up and do the first movement, make sure that your toes hang off a little bit and are ready to scoop. Pop with your foot scooping forward and kick out. Since you are going fakie you’re going to have your face pointed in the opposite direction you are going, therefore when you flick you are able to spin around better with your board.
Spinning with your board is one of the complained-about parts of the fakie backside flip. Make sure when you first pop, your arms are facing away from you. Then swing them around with the board as you jump with them. Give it the same notion as a 180. Make sure you hover over your board. Now the next moments go very fast but I will try to explain them.
When you’re in the air you’re going to have to get your timing right. You have to stomp down at just the right moment, when you think enough time has elapsed, or you can slightly see the griptape, catch the board and stomp. As soon as you stomp, you’re going to have to bend your knees way down until you have regained your balance.
One of the most common issues with people is that their board lands upside down. This happens when you probably aren’t popping and flicking the same amount, you are popping more than you flick. To to solve this you can pop less and flick more until your popping is the same amount you are flicking. This helps with rocket flips as well.
Another hard problem to deal with is when you land on the nose of your board. Although I'm pointing out the obvious when I say that you’re leaning too far forward, it can really help. The reason you are leaning to far forward is because of your 180 in the air, you are leaning too far into your 180, therefore landing on the nose. If you lean more in the center when you do your 180 then you are more likely to not land on the nose.
Congratulations you have just landed a fakie backside flip