Don't really think there is a correct way as it's whatever works for you. I've seen people with packs upside down, under and over jerseys. Just what suits you best and what you find the most effective.
I never really realised there was a technique for pack wearing aha!
I wear mine just above my waist just about around my belly button over the top of my jersey. The one thing I do often notice at the field I work at is people often wearing the packs upside down (pod lids facing up) I'm not really sure if whether they realise it's upside down or that they just prefer it that way? Maybe they're worried pods will fall out if they're facing down?