F3 covers the center and the weak side. And pressure come always from the closest player. So if F1 pressures F2 supports to strong side and F3 takes the center and weak side.
If puck is played to strong side F2 gives pressure and F1 becomes F2 by returning below the puck. if the puck is passed to weak side F3 gives pressure F2 moves to support and F1 stays on the weak side. So you need to move and face the puck and read and react.
Kai
Kai