Instead of doing normal weave with a 2-1 beat(2 on the opposite side of your body, 1 on the same side), you add an extra tight spin on each side of your body. This involves your wrists twisting more than you really think they should. You end up not tangling because when you cross to the other side of your body you end up unwrapping and spinning in the other direction.
If it does wrap around your wrist, it means that you are either not twisting your wrists enough, or letting it spin to far around before crossing to the other side. This intentional tangle leads up to the 7-beat weave, which is messy, and often involves tying your wrists together and letting them bathe in burning kero. Not of the good.
BTW: Thats what happens when you do that figure-8 cross in front of you, it doesn't look like it changes direction, from a normal POV, but if you stretched it into a flat plane, it would go from clockwise to counterclockwise to back again. It just gets extended with weave, and extended again when you add extra beats on each side.
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Luke