What's the one best how-to drill for beginners?

For helping beginner skiers who are floundering, who just don't get
the concept yet?

Let's move on a step to include those who are "working" along, maybe
some kick and glide, who are fit, but then of course flounder on the
uphills and just work too much everywhere---what's their best drill?

If you wanted to show them TWO great drills...?

I'm kinda thinking it's No-Pole Skiing.

What's the #1 snag in learning how to ski?

I suspect it might be the "hinge at the waist" arms straight forward---
no kick---too much arm work---then sliding back down any uphill.

--JP