Here are 3 ways to enhance spinal mobility. Going into flexion helps relieve tension through both the lumbar and thoracic perispinals. Progressing from hands to forearms increases the need for anterior core activation bringing the ribs down. Not only will you gain mobility but also get a nice abdominal workout in the process *Note* focus on Breathing fully exhaling going higher into the stretch with each exhale. Try going for 5 breaths at a time rest and repeat.
Bear crawls are a great bang for your buck exercise to work on close chained core shoulder stability, anterior core strength with a reciprocal pattern. One also has to control rotatory stability. Backward also works some scapular upward rotation. Start of by getting comfortable with the position. Get in a quadruped position and lift at the knees about 2 inches and hold for around 10 breaths. Once comfortable go for a stroll! Practice both forward and backward. *Add a dowel or cone into the mix and this will help improve lumbopelvic control (just don't let it fall)!
Often times we tend to extend through the lumbar spine instead of from the hips. Learning to disassociate one from the other can help improve lower back health. Here are a couple of exercises to work on. 1) Flexing the opposing hip during a Single Leg Glute Bridge will help you reach full hip extension on the working leg. 2) When performing a Bird/Dog exercise make sure to flex the lumbar spine to focus on extending through the hip instead of the spine.
Often times we lose lumbopelvic stability while doing deadbugs. This lack of control may turn a great exercise into a not so favorable one. A physioball is a great tool to create tension through the core, pulling the rib cage down promoting proper spinal alignment trough full range of motion. A good cue here would be to keep the back flat against the floor... or in this case the table.
Two easy core exercises you're not doing... and should be! When it comes to training the core musculature people often default to working the superficial core striving for those 6 pack abs and forget about the underlying deep core musculature. Anti-rotation exercises are a great way to target these deep core stabilizers and improve one's functional strength.
Here is a great progression to the Super Clam exercise used by @feldmanpt we like this variation to engage your anterior core, control rotatory stability. You get some good glute med and lateral trunk activation as well.