Here's how to do it: Place your feet as if you were about to kickflip. Start your kickflip, while it's spinning, turn your body backside to start the backside 180 ollie motion. After you and the board have turned about half way (90 degrees), catch the board like you would with a regular kickflip. Now the tricky part; after you caught the board, snap your back foot around you to finish off the complete 180. Land on the trucks, and ride away smoothly.
You can also perform this trick fakie, which is called the half-cab kickflip.
It's important to watch people perform this trick in order to get a better understanding on how to do it. This trick might take a while to perform correctly, so keep at it.