I start by asking them to hold their hands out flat, thumbs pointing at each other... the one making the letter 'L' is the left hand!

Doesn't allow for dyslexics, though...!

I would have thought strip the willow didn't work quite as well at arm's length, unless the music was slower than usual.

Often the reason for a 'correct' way of doing things is simply that it helps the dance to flow better. Getting everything horribly wrong is so much more fun, though!