The plank can be found in almost every sun salutation and is characterized, as the name suggests, by a stretched posture. This asana doesn't look very complicated in itself, but there are a few things you should keep in mind and the one or other tip will help you to keep the position easier:
From head to toe a straight line runs from head to toe - but the bottom is not too high in the air, the back is not round and the hips are not too low.
The shoulders are directly above the wrists - i.e. the straight line continues here in the same way.
The gaze goes directly between the hands below the tip of the nose (not backwards to the feet or forwards, pointing upwards)
PS: Did you know that the board position is also the other way round with the face up? Here the insides of the hands and feet are completely on the floor, the hands also point inwards to the feet and you virtually push the floor downwards away.