In response to Dr. Stuart McGill's research regarding spinal health, much of the new-age core training focuses on "anti" movement stability training: anti-rotation, anti-extension, and anti-lateral flexion. I called this exercise the "anti press" because it addresses all those categories simultaneously.
Grab the handle of a suspension strap and face sideways. Lean out so that your body is at about a 60% angle to the floor. Now brace your core to keep from twisting and press straight out until your arms are fully extended. This part of the motion is similar to a Pallof press you might do with bands or cables and works anti-rotation.
From there, bring your arms straight overhead and pause for a brief second. At this point, you're focusing on anti-extension and anti-lateral flexion. Rinse and repeat for the desired reps. Along with building tremendous core stability, this also assists with shoulder strength and mobility.
It's easy to progress or regress simply by adjusting your foot position and/or the length of the strap. The further out your feet are from the anchor point and the shorter the strap is, the easier it will be. Move your feet more underneath the anchor point and increase the length of the strap as you get better.
This is a very advanced exercise, so you may want to start with just the overhead portion and see how that goes first.