Source: https://www.skimag.com/performance/fitness/5-deep-core-exercises-for-low-back-pain
Grab a big medicine ball or stability ball and begin on the floor in a reverse tabletop position. Extend arms straight overhead while squeezing the ball between your elbows and knees. Drop and extend the opposite arm and leg while continuing to squeeze the ball between the other elbow and knee. Return to the starting position and continue to extend the alternating arm and leg. Be sure to keep your core engaged and your lower back pressed firmly against the floor throughout.
Begin in a tabletop position with hands directly below both shoulders. Lift your knees off the ground and slowly crawl forward while keeping your core engaged and back flat.
Begin by lying on the floor on your back, then extend your legs and arms off the ground and away from your body. Press the lower back into the ground as you round your upper back to create a hollowed-out position with your body. From here, rock back and forth, keeping core engaged and legs and arms fully extended.
Grab a kettlebell or any other weight that can easily be carried in one hand. With weight in one hand, slowly walk in a straight line across the room, keeping shoulders level and resisting the pull of the weight. Switch the weight to the other side to walk back across the room to the starting position.
In a standing position, hoist a kettlebell or dumbbell onto one shoulder without craning your neck. Slowly march forward in a straight line, keeping weight on the shoulder and bringing knees to hip height. Once you’ve marched across the room, switch the weight to the other shoulder and march back to the starting position. The slower you march, the more your core has to work to keep you stabilized.