Body
A fundamental body add in hacky sack and footbag freestyle.
Demonstration of a Duck.
Set the footbag slightly higher than head level to give yourself enough time to move around it.
Move your head to the opposite side of the footbag's path as it passes, rather than trying to move the bag around you.
Keep your eyes on the footbag as you move underneath it and stay balanced so you are ready for the catch.