The flex defense is probably the most used defensive formation that I use during a game. Mainly because it can be incorporated into any defensive scheme used to block any shot.  It works fairly well against  most shots, especially when the shooter isn't very good. The good thing about this formation is that it can be used at both the goalie and forward position. It can even be incorporated into a zone defense.

The idea behind the flex defense is to expose a portion of your goal to the shooter while using a normal defensive formation to cover the area at the location where the shooter has the ball. Just before the shooter executes the shot, you move or shift one or both your men to cover the exposed area of the goal in a very subtle way.

Here is how the flex defense works
While the shooter is setting up to do a shot, place a typical defensive formation between the spot where the shooter has the ball and your goal.

Here the defense is set to stop a pull shot.

In the example above, the defense is guarding against a pull shot. This defense should work well against the short and the straight in. But, against the long pull, there is good chance the shot will find its mark against this defense. This is an ideal situation for the shooter.

When you feel that the shooter is about to do the shot, move the back man towards the exposed portion of the goal, and move the forward man slightly toward you. All the while, you want to be reading the body language of the shooter to determine when he will execute the shot. Also, you want to be observing the shooter to see whether he is paying attention to your defense while you flex your defense.

be very subtle when doing the flex

The thing about flexing your defense is that you want to be as subtle as possible. Sometimes, you may wish to flex into different position before you finally set into a position of your choosing. This is to keep the shooter guessing. The trick is to be very subtle. While the shooter is preparing to shoot, flex your defense in one to three seconds intervals, and remember to be as subtle as possible.

Try this technique out and see if it works for you. Remember that this is not a sure way to stopping any shot all the time. The flex defensive concept is a good component to use in your bag of tricks for protecting your goal. And like anything, it is going to take time to use it proficiently. Do not get discourage if it doesn't work the way you want it to. Practice using it and mixing it into your other defensive schemes. I believe you will find it to be very beneficial.