This stretch is for your side/lat/back and is a little more complicated, because it is only really effective if you are in a good position. This can be done either in a sitting or standing position, so use whatever position feels best to you.
Start by taking the hand of the side you want to stretch and grab your opposite leg. When doing the standing version, grab just below the knee and during the sitting version, grab just above the knee. These are just starting points and the goal is to find the place on your leg that gives you the most leverage and the best stretch.
To perform the actual stretch, pull against your leg with your hand and simultaneously arch your back/side and try to push your torso as far from your leg as possible. You will not actually move very much, but the act of trying to bend and push away should create a good stretch down your side/back.