The lower you set the machine, the more emphasis is put on your low-back/spinal erectors.
At the top, make sure your spine is in a neutral position
Ribs stacked on top of your pelvis.
Your back is neither arched or rounded.
Cross your arms across your chest or behind your head.
Your legs are passive in this movement.
No excessive momentum or upper body swaying.
Slowly let your low back round and descend your torso to the bottom position.
Don't fall or drop to the bottom.
This is a controlled movement.
This is the one exercise you don't want to actively hinge your hips. Keep the stimulus on your spinal erectors.
Legs and hips are passive.
At the bottom, slowly raise up without generating momentum from the rest of your body.
Create the mind-muscle connection of your low back controlling the exercise.
Your top finished position is neutral spine. Don't arch your back at the top or the starting position.
*Tips*
The legs are remaining inactive. This is one of the few exercises where you want to stress your low back/spinal erectors.
Before adding weight, manipulate the tempo of the exercise execution add a new stimulus. This is much safe than progressing holding plates, barbell, DB's, etc...