Your muscles provide a stabilising role to your spine and surrounding joints. Weak core muscles mean your spine has to endure more load and stress, this is something you NEED to address in order to have a healthy spine. This video demonstates the side bridge exercise which helps improve your lateral flexor endurance, whilst creating optimal tensile load on those muscles and minimal compressive load on the lumbar spine.
Lateral flexion of the torso or body means leaning to the side. The muscles primarily involved for this movement are the internal and external obliques, quadratus lumborum and erector spinae. I would advise doing 3 sets of 10 repetitions. You should start with in your tolerance range, and increase sets accordingly. These exercises can be done every couple of days, and then daily once they become easier.
