If you have lower back pain, instead of working on your abs (or rather than just working on your abs) something you should consider is working on your hip joints, with standing hip exercises while balancing on one foot.
7 Hip Mobility Exercises For a Full Range of Motion - Welltech
Stretches and Exercises to Strengthen Hips, From a PT
Exercises for the hips
Standing Hip Dip — Rehab Hero
Standing Hip Extension: Tips and Recommended Variations
Butt - Standing Hip Extension with Short Resistance Band - FIT
8 Hip Flexibility Stretches for Tight Hips
12 Best Stretches for Hip Pain Relief [FREE Exercise PDF]
Standing Hip Abduction - Ask Doctor Jo
7 Essential Hip Flexor Stretches
9 Standing Exercises You Can Do at Work or While Waiting in Line