Stand beside a wall with the arm extended at shoulder height, palm flat on the wall and open the chest. Can be done with elbow at 90 degrees. Hold 5 breaths/side and repeat 2x.
You may also do both shoulders at the same time by using a corner, bending the arms to a 90 degree, palms onto walls, drawing chest towards corner. 5-10 breaths.
Bend one arm and bring the palm of that hand towards the middle of your back. Draw the elbow towards the midline of the body and backwards keeping your neck and neck in neutral alignment. Hold for 5-10 breaths then switch sides.