Stand in front of a bar (or another surface that is stable and will not move - kitchen counters also work great for this).
Walk the feet back, perform a hip hinge and pivot forward until you feel so resistance to the movement in the thoracic spine. Hold this position for 5-6 seconds. Repeat as needed.
NOTE: this may cause the back to crack. Not getting a crack in the back does not mean the movement was ineffective.