Would you share your core strengthening plan?
Unfortunately the program part is a paid membership. I'm only about 2 steps into it right now. It's not difficult but it's specific and a bit hard to explain. I'll try.
Imagine this flex done while standing, on your back, hands and knees, and then the plank he shows. What I did last night in each position was flex the top 5 times, holding it for a long exhale. Then do the bottom. Then do both at the same time. So 15 total reps in each position. This is the one he starts with and it really helped.
The program is about 9 steps that each address a specific movement/muscle groups. This is part of the first section. The second section works the erectors, back strap, upper and lower sections.