Set up cones and let B2 know that is the space they need to cut into. Also let thrower know that is the space they need to throw into.
B2 fakes a strike cut. And comes dump in the direction of the box. The most important skill in this drill is being able to chop your feet, plant and change direction on your cut.
The thrower needs to pivot, open up their body to the space they are throwing to and execute a throw into that box that takes a path away from the dump defender.