"Seated Forward Bend" modified with a strap is a great pose to stretch your whole back side from the feet to the neck.
From a seated position with your legs straight out in front of you, have a strap or belt on the floor just in front of your feet and next to your legs. Flex your feet with the toes pointed toward the ceiling, don't let the legs open. Have as much of the backs of your legs on the floor as possible. Now either scoot your sit bones back a little or give yourself "butt pulls" by placing a hand under one sit bone pulling it back and then do the same on the other side pulling the sit bones back. This gives a mild anterior tilt to the pelvis helping you to forward bend in the "Seated Forward Bend". Place your hands beside and just behind the hips pushing into the floor and lengthen your spine as much as you can.
Now grab the strap next to the legs and position the strap at the front of the arches or on the balls of your feet. Begin by pivoting from the hips without rounding your back or dropping the head. If you notice you have minimal to no movement in the hips it's probably because your hamstrings (upper backs of the legs) are tight not allowing any movement in the hips and minimal movement in the torso coming forward into the forward bend. This is not a problem and is common for beginners. To help you pivot in the hips place a folded blanket or towel under your knees taking tension off the hamstrings. The problem is you may have tight hamstrings and they are pulling on the sit bones (ischial tuberosity) that are attached to the pelvis. This prevents the hips from tilting forward into a forward bend. So the blanket or towel lifting the knees takes some tension out of the backs of your legs so you can have a little movement in the hips. What your working on is tilting the hips forward over the heads of the femurs (top of the upper legs where the ball is attached).
Keep the spine straight the whole time. Our focus is in the hips, once you get some flexibility then you can round your back a little. A good forward bend is 2/3 hips and 1/3 rounding back.
Hold the pose 30 seconds to 5 minutes with a hospital pain level 5 or less. As long as you're pulling and your pain level is 5 or below you can hold the pose 1 to 5 minutes to stretch tight hamstrings.
Benefits: Stretches the hamstrings on the upper back of the legs, stretches and lengthens the back and spine, massages the internal organs, helps with sciatic nerve issues as well as the nervous system. Improves digestion.