Start by getting into a normal Plank position, making sure to lightly protract your scapula and engaging a posterior pelvic tilt to have a straight body.
Swing your hips sideways until they make contact with the ground. In a continuous motion, repeat for the remaining side. Don't lose the posterior pelvic tilt and scapula protraction during the hold.
Keep repeating this movement until the time goal is achieved.
Progressions And Regressions