One of the common problems and query pertains to strictness in sitting postures and difficulty in maintaining those postures due to uneasiness, pain in the knee or tickling sensations that some people feel in different parts of the body or simply due to fluttering of the mind. While most wisdom traditions have maintained a certain cross-legged posture and straight back for good reasons, as it helps in energy to up higher smoothly. Keeping the back straight is also a common principle in forms of martial arts, thus clearly pointing its merit and need

However, from own experience, meditation is fundamentally about making our mind sit down and thus slowing down the rate of thoughts. My personal recommendation is that do not make posture as a task in itself but rather sit comfortably in a cross-legged position, so you are not fidgeting around or suppressing inconvenience. If you are not comfortable physically it becomes increasingly difficult to calm the mind down. The key in meditation is to feel relaxed. As the mind calms down, making course correction in posture is easier as you would have tasted meditativeness by then

Using principle described in section 3.1, can also help in making sitting easy. There have been numerous meditation masters that have used alternative positions for meditation eg) Mahavir and Tilopa practiced meditation in a standing position and Meher Baba would lie down and meditate. People who are old and find it difficult to cross legs can also meditate by sitting on chair, but the key is to feel relaxed and to be able to calm the mind

In case you use a relaxed sitting position instead of classic position, my personal recommendation is to end the meditation by lying down straight on your back for 5 minutes with closed eyes and in relaxed demeanor. This will give you the benefit of unobstructed energy flow.