Read Maty Ezraty's response:
When students are stiff and have a lot of work to do on opening their hips, I tend to be very sensitive and encouraging. It can be humiliating and frustrating to sit on many blankets and feel like the pose is years away. Some students just give up the practice.
Therefore, I try to give them other poses to work on. That is not to say that they should stop sitting in Sukhasana on blankets. But they can work on the external standing poses, which are critical to opening the hips. Teach them Vrksasana (Tree Pose), Utthita Trikonasana (Extended Triangle Pose), Virabhadrasana II (Warrior II Pose), and Utthita Parsvakonasana (Extended Side Angle Pose). Other standing poses, such as Virabhadrasana and Prasarita Padottanasana (Wide-Legged Standing Forward Bend) are also helpful.
You may also want to add poses that are reclining, so that it is easier for your students to relax while working on the hips. For example, Supta Padangusthasana (Reclining Hand-to-Big-Toe Pose), using a belt and lifting both legs straight up and then to the side, is helpful. When taking the leg to the side, you may need to prop it on a chair, a block, or the wall.
When their hips begin to open, then you can introduce "Thread the Needle," either lying down or against the wall. The restorative pose Supta Baddha Konasana (Reclining Bound Angle Pose) on blankets is also helpful. If the student is experiencing pain in the knees, it is because the knees are high off the ground. You can eliminate that by placing blocks or blankets under the thighs so that the knees are propped.
Be encouraging with stiff students, and give them poses that can help them see the hope of gradual progress. With patience and perseverance, you and your students will both gain wisdom in this work.
Maty Ezraty has been teaching and practicing yoga since 1985, and she founded the Yoga Works schools in Santa Monica, California. Since the sale of the school in 2003, she has lived in Hawaii with her husband, Chuck Miller. Both senior Ashtanga teachers, they lead workshops, teacher trainings, and retreats worldwide.