How to do a shrinking jab

simultaneously plant the foot forward and extend the arm.

"Gotcha!" Shrink back immediately after, ready to follow up. As the foot plants, it is also turned outwards (outside edge facing opponent). This will assist driving back to the normal stance.

The turning of the foot allows for increased rotation of the body. Imagine pushing off the opponent as you drive in with the punch. Foot is grounded for stability. Heel and outer foot tread forcefully

As you shrink back you could cover the chine with the shoulder, and face with the right hand.