On hands and knees on a flat surface. First arch the back like an angry cat, then drop the belly towards the ground so the back stretches downward like the angle between the humps of a Bactrian camel.
Seated upright (no slouching) with hands behind the head. Side bend and then rotate towards the side you’re side bending.
Seated on a flat surface, legs in front, cross one leg over the other with the knee bent. Rotate the torso keeping the back straight towards the side of the crossed leg. Gain an extra stretch into rotation by gently pushing off of the bent leg with the front arm and off the floor with the rear hand.