This ball screen flat switch basketball drill is simulating a big man flat switching out onto the ball handler. The big man knows that he/she is not as quick as the ball handler, so they are going to sit right below the 3 point line and give space and time for themselves to react.
Tony Parker is one of the best players at using this move, but what you are going to do is back up, get a running start at the defender, and then make your move to go past the big man to the basket. Don't play with the basketball when you make your move, but be efficient and attack aggressively at the big man. It is important that you know the different basketball fundamentals of using a ball screen, and are prepared for any type of ball screen defense that the other team throws at you.