Thanks to Kristen Byrnes for posting the actions to this song on the Guide Mailing List!!
Sitting cross-legged in a circle, each person places their left hand face up between their left knee and their neighbour's right knee about a foot off the ground. Everyone places their right hands, palm down, on their right neighbour's upturned left hand. To the music (so these actions fit half of one line of the song) with your right hand, first you hit your neighbour's left hand, then your right knee, your left knee, the bottom of your left hand and then the top of your left hand twice.
E.g.: for the line "Edelweiss, Edelweiss", you'd go through the actions twice.
The really hard part is switching directions. Usually initially the switching starts at the word blossoms (from Blossoms of snow... ) so your left hand is now doing the hitting and the right hand remains stationary. Once they and you feel comfortable with that you can switch every time (therefore you'd switch twice a line).