Observe the breathing mindfully, laying down. Observing the flow filling the abdomen, ribcage, chest/back. And exhaling from the top down releasing the air in the chest/back, ribcage, and abdomen
Observing the two stages of diaphragmatic breathing (abdominal) and thoracic breathing (chest and back). Pausing between each stage, before exhaling and releasing the air in the thoracic cavity, and finally releasing the air in the abdominal cavity. Observe the two stages.