From Reverse Triangle, lift the torso up, bend your right knee and lower both hands to the front of your mat. Lower your left knee to the floor, pointing the toes.
Slowly lower your right knee to the right so you're resting on the outside of your right flexed foot. Keep your arms straight, pressing your chest forward just like in Upward Facing Dog. This will help encourage your hips to lower, increasing the stretch in your left hip flexor.
Gaze forward, and enjoy this pose for five breaths.