Here is the collection of anime sitting poses. These are poses in which a character has a part of the lower body partially or fully collapsed. Think kneeling, squatting, or just relaxing.
Use:
If you're learning, that's what the two sets of lines are for. Blue is the underlying structures of the figure. While the red is the skin line that is not covered by clothing.
If you need inspiration, I hope one of these poses will provide it for you.