The couch stretch is great for opening the hips by stretching out the quads and hip flexors. The main thing to remember with this one is that quite often people will be tight through these muscle structures so it may not take much to get that stretch happening. Each time you do it, try and increase the angle and positioning! This stretch is great for doing against the couch (hence the name) and also against a flat bench in the gym. Pop a rolled towel or pillow under that knee for comfort!
Due to so many people being in a seated position for many hours of the day, the hip flexors (Tensor Facia Lata and Psoas Major) tend to get a bit tight and ultimately can cause the pelvis to tilt forward which can lead to lower back tightness and soreness. This neat stretch can help stretch those pesky hip flexors out and avoid the tightening happening in the lower back!