Everyone has their own way of holding socks. Personally when I actually used my stretchies I didn't like this kind of hold as I felt is restricted my ability to change holds mid spin, which I do a lot for different moves.
Knots are your friend, you just have to do them right. For these kinds of socks you don't want a knot out in the middle, you want the end to be knotted. It may take a few tried to learn to tie it right but basically you want to tie 3 knots, one over the other, in the end. I DON'T mean sequentially. I mean literally OVER (around, covering) each other so you get one fat knot. 3 was the way I did it, if you have bigger hands tie 4.
Once you have your knot, hold your hand out palm up. Pick your favorite 2 fingers and rest the knot at the spot where the fingers join your hand (right on the webbing). close fingers together. Now as you spin you can wrap, unwrap, change fingers etc whenever you want without worrying about throwing the poi.
Just another option for ya
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I once learned every move that there was,
Every style, Every technique.
Then I woke up, and forgot it all,
So now I struggle to dream.