Source: I've been a level 3 snowboard instructor in Canada for 10+ years. There are only 4 levels.
It also doesn't work if you're with a group of students because it won't be a surprise after everyone sees you do it to the first student. If you have a "slide on snow" competition but don't say why, you can watch everyone and what foot is forward before you tell them what is going on.
I tend to default to right foot forward for most things. Sport fencing did it, maybe…
Everything felt absolutely right, UNTIL I gained some real speed for the first time. Nope! Suddenly everything felt wrong, and I instinctively turned so I had my right foot forward.
So weirdly goofy it is.
I kick the ball with the right, and on the boards sports I'm goofy.
But when I try to imagine myself standing on a skateboard, it gets clear immediately: left foot forward. Right foot forward feels completely wrong.
Close you eyes and really imagine it (or do it right now). Really feel yourself sliding along, that tingly feeling of almost losing control, etc. etc. Going a little further with each try.
REALLY run and slide AS FAR AS YOU CAN.
Which foot did you have in front?
I'm very much right handed and footed in life, but in this test I can really only do it right foot forward (called 'goofy' in snowboarding) - left foot forward feels super sketchy to me even after years of practice, and I can't slide nearly as far.
The vast majority of people (left and right handed) are left foot forward.
(This is the best way to determine which foot a beginner should put forward on their snowboard or surfboard. Do the test without telling them you are doing the test. If they can equally do both, then it doesn't matter)