Why?
The wide base protects the ball from a player (pressure) engaging from behind – see video
2 – Post Up
The post up is not one fluid movement (it just looks that way with practice):
Why?
The post up is a key skill to offer the ball carrier a pass to you and allows you to protect the ball from the defender who is tracking you.
3 – Receive in flow
Your feet should be facing the intended direction of travel.
Why?
Not having to secure and then move the ball and turn your feet to carry the ball off makes for faster hockey and less time for the defender to engage you.