Updated: Jul 11, 2020
So once you've mastered level 1 and ready to move on, here are what I would call 'level 2' exercises to progress you in your core work.
There are 4 exercises:
Alternating heel taps (6-10 reps each side)
4 point kneeling 'core breathing' (10-15 breaths)
4 point kneeling leg slides (6 - 10 each side)
Breath and ball squeeze - lying or standing (10 btw hands, 10 btw knees)
Do 1-3 rounds. More if you like!
Here is an instruction / follow along video: