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)