This throw is used against a straight punch and is nearly identical to the Cross Hock Throw.
As your attacker throws the punch, block the strike with a basic inside forearm block and step forward and to the left with your left foot. Your foot should be next to your attackers right foot.
Use a ridgehand strike to your attackers main artery in their neck. A powerful strike here will cause them to nearly pass-out.
Now push on your attackers left shoulder to take them off balance. This will make the throw much easier.
Place your right foot on the back of your attackers right knee, this foot will be used to sweep their leg forwards.
Push with your right hand on your attackers shoulder and thrust your right foot backwards to sweep their leg. Once they are on the floor you may finish with a strike or arm-lock.