The mechanisms for hypertrophy are the same whether we’re talking about biceps or abs. You’ll need to combine high-tension exercises, create metabolic stress, and create muscular damage. The kneeling cable crunch takes care of the latter two.
Kneel while holding a rope attachment on a pulley at eye-level. With the sides of the rope held next to your head, push your hips forward, extending your hips and stretching your abs at the top of the movement before flexing at the waist, squeezing your abs as hard as possible at the bottom.
This isolation exercise will maximize your muscle-mind connection. As with all isolation exercises, use a long time under tension to create metabolic stress. Take a one second pause at the top, three to four second eccentric (negative), a slight pause, and a two-second concentric (contraction phase).
Stay focused and let your abs do the work rather than going fast and using your arms.