Inside control is a concept you'll hear again and again at good jiu-jitsu (and wrestling) gyms everywhere. When you're wrestling on the feet, you generally want to control that inside space, and a prime way to do this is to swim your hands inside your partner's biceps. Of course, your partner will know this rule as well, so as they go to pummel back inside, take the opportunity of their elbow circling inward to push their elbow even more inward, making them want to push outward. Use this reaction to allow your partner's elbow to lift up, opening space for you to get underneath their elbow, and in the direction of their back!

For this variation, time the duck under (dipping your head down underneath their elbow/triceps) to coincide with a lateral hop with both of your feet, ending up exactly where you need to be to get onto your partner's back.