If they aren't already, bring the hands to the floor about shoulder width apart.
Step back with the left foot into a lunge maintaining hip width between the feet, both feet pointing forward.
Keep the knee of the right leg over the ankle. Do not allow it to fall to the side or to go beyond the front of the toes.
Try to feel a line extending from the heel out through the head.
Lunges can be done with the knee on or off the floor & with the toes curled under or with feet pointing backwards.
You could include a half pyramid at this point to stretch the hamstrings, before moving into the plank pose.