Place a Short resistance band around your thighs, right above the knees.
Sit against a wall, with your hips at knee level, a 90 degree angle at the knees, and your back flat against the wall.
Use your Glutes to pull your knees out, fighting against the tension of the band.
Maintain this position for time.
Form tips
Let your arms hang loosely by your side; do not use them to exert pressure on the wall or on your legs (that would decrease the stimulus from the exercise).