LG should actually be LN - you’re sitting in the intended and expected position of the chair, following the rules of the chair design to a T. LG would probably be the same position but scooched to one side of the chair so another person could sit, and LE should actually be the same position as well but with a manspread.
Do you sit everywhere cross-legged, and are you shorter than average?
I find this is most often done by people at least one standard deviation below average height. I’m one of those people. My feet don’t touch the ground sitting normally in normal chairs, and it puts pressure on the back of the legs, making cross leg much more comfortable.
Sitting with your butt on the seat cushion seems the lawful option to me, it's being used in the normal, expected way. So sitting however you like - on the arms or top, feet on the seat, upside down would all be chaotic.
Spreading out and taking as much space for yourself seems like the best analogy for evil. Since good is about considering others and the wider consequences, I would think of good sitting as sharing the chair or at least leaving room for others.
I think chaotic good is perfect.
Lawful evil (the evilest alignment) sitting should be full man-spread, a pouf for each foot, giving both fingers to a bunch of tired looking children.