ABS

Pilates

You first have to reduce your body fat to a level where the muscle will show through. This is only done with a calorie deficit and exercise. Once you get to a decent bf%, weight lifting affects your core is best...not specifically "ab exercises" necessarily, but I like squats, deadlifts, and push-ups. These exercises will tone your whole body, but if you do them correctly without the use of weird machines in the gym, they will tighten and strengthen your ab muscles too.

When I was in my best shape(which was pretty amazing), I did not have a six pack.
There is a genetic component that not everyone has.

I believe as a minimum, you have to be very lean and work your abs for about an hour a day.

Working out abs is not a requirement to have a six pack. I've got friends who are swimmers and runners never and do not do ab routines, yet have 8 packs. I had a six pack in jr. high before I ever started working out, it was because I was super skinny though.

What kind of weight lifting you meant? I do weight lifting and kettlebell workouts, but doesn't really feel in my abs

You first have to reduce your body fat to a level where the muscle will show through. This is only done with a calorie deficit and exercise. Once you get to a decent bf%, weight lifting affects your core is best...not specifically "ab exercises" necessarily, but I like squats, deadlifts, and push-ups. These exercises will tone your whole body, but if you do them correctly without the use of weird machines in the gym, they will tighten and strengthen your ab muscles too.

Compound, full body moves...squats, deadlifts, push-ups, etc. Not isolation moves like curls or kickbacks. If you lift HEAVY, then you are affecting your abs doing those movements.