With the help of a good nutrition program and a calorie deficit you can lower your body fat percentage. If you get below a certain bf percentage your abs will start showing. Everyone has a different shape of abs, this is genetically decided. Some are symmetrical some are crooked, some people have an 8 pack others have 4 packs. Thats something you can’t change.
Besides lowering your BF percentage you can train your abs to ‘pop’ more! Treat the abdominals like any other muscle in your body. If you want to make them grow/get more volume, you need to hit them with hypertrophy workouts. That means a rep range between 8-12. Heavy lifting!! Forget about the endless bodyweight crunches and start adding weight to your exercises.
Even though your Sixpack is 1 muscle you can split it up in 3 parts; upper, middle and lower.
Hit the upper area with a weighted crunch, cable crunch and on the ab machine.
The middle part is always participating, with the upper and lower exercises. The decline bench, where you hook your feet and hold a weight to your chest targets the middle in a good way.
Lower abs: all leg raises and leg pulls.
Train the serrates and obliques by doing Russian twists, plate swings and windshield wipers (for the advanced)
Don’t confuse ab exercises with core exercises. Core stability exercises won’t make your abs grow. They will improve your form, but that is a subject for another day.