This is, to me, a fundamental that needs encouragement. It involves choices and decisions. It's a part of learning how to define the game. It's a decision making game to be successful. First, they must start getting the skills necessary to play this way.
Basic tool is ball control.
Coever exercises explained within exploitation of space. Then, after and during games, gently coach them as to how the game went thru periods of differing styles. And perhaps, a small 2 man or 3 working group with a few tactical interactions. Point out how they naturally adopted their play to the changing circumstances. When a dangerous opponent got the ball, probably Will came over to help his friend to defend.