Occult, Esoteric, Magick, and Paranormal

Posture doesn't matter that much.

Just get comfortable, and don't hesitate to shift your position. Once you get good enough at concentrating, nothing you do or don't do with your meat suit can interfere. You can meditate while doing house chores, while walking, etc.

If you specifically want to get so deep that you lose consciousness of your meat and bones body then the best position is laying on your back, head tilted to the side to minimize snoring. Then you have to guard against falling asleep while still being deeply relaxed. Sitting makes it harder to fall asleep, which is why it's used often.

So just sit however, but likely you'll need to shift as pain starts to build and as blood flow may be less than ideal in places, so you would shift to let fresh blood flow and to alleviate some discomfort, and none of this bodily 'housekeeping' should take you out of concentration, which sort of runs in parallel.

I mean if you are hardcore and stubborn, you can learn to control your meat body so that it's more flexible and doesn't develop pain spots. But that is way out there and not necessary for most meditations. On the other hand if you meditate specifically on the body and on self-control within the body, then at some point it will grow naturally to where what used to be uncomfortable no longer is, and you can get your body to behave more to your liking.

A lot depends on why and what for are you meditating. Are you after wisdom? Health? Peace? Memories? ESP? Supranormal powers? Expanding awareness and control of your energy body? Projecting? Sitting may not be the best posture in all cases. Moving/adjusting the meat and bones during mediation may or may not be OK. Mastering the body may be the whole point or it may be a detour, depending on your objectives.

Moving the body is best avoided in only two cases, as far as I know: projecting, or you want to go beyond the tether so to speak, it's a state where the meat and bones body is irrelevant and will fade out. So moving is largely OK.

The most important point is that you are you. Meditation exists for you. You do not exist for meditation. Don't lose what's important.