Practice with caution to avoid injury
Flick the fists outward to both sides as you take a step to the side. Then, swing the arms to cross in front of the torso as you step across to an x-stance. As you drop down into the stance, chamber one arm, and perform a downward block with the other arm toward the direction you stepped away from.
The basic blocking system is used to teach the beginner how to defend against various attacks. The blocking system is also used to develop the student's strength and functionality. Once the core understanding of the technique is achieved, it evolves with the practitioner's understanding, later encompassing striking, joint-locks, etc..