You can assume it anywhere. It differs from the passive sitting position in which you lean against the back of the chair. At home, you can best do this in an armchair, if possible, resting your head against or on top of the chair back. The arms should rest easily on the arms of the chair. The legs must not be crossed, because this may interfere with the exercise.
Most people prefer to exercise while lying on their backs and with their heads slightly raised.
In this position the elbows are slightly bent, the palms of the hands rest next to the thighs or slightly angled away from the body. You may put a pillow under the shoulders. The feet should point slightly outward. If they point upward, this means that you are not relaxed. Not everyone finds it easy to practice while lying on the back.