When your back is taken you are at an extreme disadvantage compared to your opponent. Right away you want to defend your neck. This includes defending against lapel grips. We want to fall to the non choking side. When applying the gi chike it is beneficial to have the choking hand move towards the sky. Falling to the underhook side blocks this from happening. Once fallen on that side continue to defend against their attempt for seatbelt control.
Once youve fallen to the non choking side, begin to pry your opponents bottom hook out with your bottom hand. Keep your shoulders to the mat and after prying the bottom hook slide over their leg. This will allow you to turn into them, landing in half guard. Often your opponent will counter this by pressing into you and you end up in Bottom Half Guard.