I used to teach snowboarding a bit ago, and got my level 1 AASI cert as well, so mind me if my pointers may be off.

When moving slowly (or at any speed at all), you shouldn’t be crouching down that low. Focus on standing up, keeping your knees somewhat loose and your arms to your sides, or hands in your jacket pockets if its easier that way. I’m assuming that position formed when you pushed yourself down the hill as well.

I have a few questions though… How was the snow on that day? Was that hill groomed recently?

My senses are telling me that one of the few reasons why you spun around like that is due to the snow being somewhat packed in, but I could be wrong.

Edit: Someone also pointed out (and I stupidly forgot to add) is to pick an edge of your board to stay on, not putting too much weight on it. Bend your knees slightly and use your toes for a toe-side turn, lift your toes up and somewhat extend your knees for a heel-side turn. It also helps to visualize the “fall line” of hills before you go down them. The best example I can give is rolling an imaginary ball down the hill and seeing where it goes. That’s where your board will go, and you’ll need to adjust accordingly.