Extended side angle pose (utthita parsvaokonasana) can stretch the side of your torso and your thigh muscles depending on your body position.
I’ve previously written a step-by-step how to for extended side angle pose.
It has many variations from gentle to extreme. While it’s common to see the hand on the floor in this pose, it’s rarely possible for most people to do this safely. It requires significant flexibility in your hips and back. If you lack that flexibility you will bend forward, torquing your back and losing the side stretch.
To master this pose is to find the side body stretch and that will be easier with your elbow on your thigh versus your hand on the ground.
This video goes through the basic body position or alignment with some tips on finding the side body stretch.
