More fun with a Theraband for stabilizing the hips & low back.
Using the same heavy resistance band around the shins, slightly bend your knees. Check that both hips are facing straight ahead and tailbone is drawing down to the floor so there's no arching in your back.
Step one foot directly out to the side without letting the hips tilt. Step the other foot to meet it without letting that foot drag or slide on the floor.
Go back and forth a few times, aiming for about 30 reps.
For the second variation, step the right foot out to the side and behind you. Step the left foot to meet it. Then step the left out to the side and back. Make the movements as big as you can without moving the hips or arching your back.
Now reverse the motion, stepping the feet forward and to the side.