The English concertina no doubt likes best being played standing. It is symmetrical, held between the hands similarly, relatively light, and its dynamics is best performed while standing. Tutors however mostly recommend that it be played sitting. They often suggest that the bellows are worked with one hand while the other end of the instrument is resting on the knee. This will often unnecessarily wear out both the clothes and the bellows.
Some tutors suggest hanging the instrument from a cord around the neck.
Anything hanging around the neck is liable to cause tensions, and if the cord is not elastic the elbows will be kept in a static angle, which is unsuitable. A better idea would be hanging it from the front ends of elastic braces. This would relieve some of the weight of the instrument but you still can not grip it safely. You are supposed to do this by means of a thumbstrap and a little finger rest, two sophisticated implements of torture. The thumbstrap, if set tight enough for full control of the instrument will first make your thumbs ache, then getting numb and if not released threatened by gangrene.