Back Step to Knee Slice

Addressing the issue of an opponent's underhook in the half guard, particularly when they prevent closing the distance in the Angry Bird position:

1. As the opponent secures an underhook and attempts to push forward, make a grip to prevent them from using it to their advantage.
2. Execute a back step, pushing the leg back and landing with the foot planted on the mat and the heel close to the buttocks, similar to the reverse De La Riva position.
3. From this position, you can choose to stay and establish control by grabbing the gi and applying shoulder pressure.
4. Prevent the opponent from placing their leg on the mat by gripping the top of their leg.
5. Transition into a knee slice position by lifting up, diving under for the underhook, and grabbing the opponent's leg.
6. Shove the opponent's leg down while taking a large step to gain momentum and rotate back into the knee slice position.
7. Ensure your knee lands on the mat, then grab the opponent's tricep, push through with your hips to the mat, and apply shoulder pressure.
8. Finally, place your knee against the opponent's hip, replace the grip with your hand, and establish side control.

It's important to make a large step and rotate to avoid getting caught by the opponent's legs, maintaining hip position, and creating space for the transition.