As you sit slightly forward on your chair, twist your head and torso to the right. Then cross your left arm to reach the arm rest at the right side of your chair. You can modify if it’s a bit difficult by reaching the side of your right knee instead.
As you do the maneuver, make sure to keep your feet flat on the ground. Also, you can rest your right hand on top of the back of your chair.
Hold the position for 20 seconds, then switch to the other side.
This stretch will help in reducing the feeling of stiffness on your back.