As the name suggests, seated meditation https://www.julianalucky.com/yoga-for-kids is practiced while sitting. A certain posture is not as important as the general principle of staying still for a while.
When you sit still even for 10 minutes, the mind is refreshed. During longer meditations, the physical body goes into rest and recovery mode and benefits from a good night’s sleep. When the physical body is still, you may notice subtle movements of energy and mind. Ideas are more clearly understood.
In an air-conditioned room, our ears fill with its hum. But when we turn it off, we are suddenly aware of the ticking of the clock, which has been lost all this time in the hum of the air conditioner. Stop the clock and now you are aware of the sound of your breath.
Sitting meditation works in a similar way. You position the physical body in such a way as to facilitate the cessation of gross levels of movement. This allows you to notice other things: the rhythm of breathing, the beating of the heart, the movement of subtle energies and thoughts. Then you start noticing the one who is noticing. Who is it?
The motionless position of the body for meditation can also be taken standing or lying down. If you find it difficult to sit because of an injury, there is no problem. Find a pose that works for you. It is good to alternate the practice of motionless meditation with dynamic meditation techniques: qigong, yoga or walking. 
Over time, contemplative methods in motion will help you feel more deeply about sitting meditation.
In the process of exploring sitting meditation, you will find the most comfortable position for you. If you have enough flexibility, you can sit straight on the floor. There are several most suitable positions for sitting meditation. These are the easy pose (sukhasana), the hero’s pose (virasana), the perfect pose (siddhasana), the half lotus pose (ardha padmasana), the lotus pose (padmasana).
It is also good to sit with a straight back on a stool or chair, without leaning against the back, so that the spine is pulled up. Alternatively, you can place pillows between your back and the back of the chair. The main thing is to choose a position in which the body will feel relaxed. Sitting is a very good way for beginners because an upright back keeps you mentally active. But you can practice meditation in any position. Find what works for you. The initial set-up for the meditation process is the same whether you are sitting on the floor, on a cushion, or in a chair.