This technique was contributed to Lockflow.com from the guys at CMU Grappling club. You can visit their site at: CMU Grappling Club Check them out!
According to CMU:
"It is essential for every martial artist to know how to escape the mount position. Even if you prefer to strike from standing, it is very possible that you may end up mounted if your opponent clinches with you and manages to take you down. The mount is a natural position and one that even an unskilled opponent is likely to obtain if given the chance. Even someone with zero martial arts training can easily knock you out from the mount position. Therefore it is essential to know at least one escape from it, even if you are not primarily a grappler. Below you will find a simple and effective escape from the mount."
Xander has Randy controlled in the mount position. He is sitting on top of Randy's chest with his knees pushing into Randy's armpits. Xander squeezes his knees together for control. From this position Xander is able to apply a large number of submissions or deliver powerful strikes to Randy's face.
Randy wiggles his body from side to side and uses his elbows to push Xander's knees closer to his hips. Xander is now sitting on Randy's stomach rather than his chest. This allows Randy to better defend Xander's strikes and sets up the next part of the escape.
Randy pulls his feet into his butt and bucks Xander forward using his hips. This motion disturbs Xander's balance and pulls his body close, taking away his striking ability.
Randy uses his right hand to grab the back of Xander's head. Randy pulls Xander's head into his chest to further break his balance
Randy uses his left hand to overhook Xander's right arm from the outside. Randy does this by placing the palm of his left hand into the crook of Xander's right elbow and pulling downwards towards his hip
Randy uses his left foot to trap Xander's right foot. Randy does this by placing his left foot outside of Xander's right ankle and pulling inward. Randy uses the heel of his left foot on the outside of Xander's right ankle
Randy bridges by raising his hips into the air and rolls Xander over his left shoulder. It is important to note that Randy does not throw Xander directly to the left. This requires quite a bit of strength and can be difficult if the opponent is much larger. Instead Randy throws Xander up and to the left over his left shoulder. Throwing the opponent up and to the left is the most important part of the technique. Even extremely large opponents can easily be thrown in this manner
Randy completes the escape by rolling Xander onto his back. Randy sits with his knees on the ground and establishes a solid base. Xander establishes the guard position by wrapping his legs around Randy's body, crossing his ankles, and raising his head off the ground. Randy has now escaped the mount and is instead in Xander's guard