Ok.
Your abs, big or flat, will ONLY show if you DONT have excess belly fat and thats final. Strongmen have HUGE and POWERFUL abs, but are fat as whales, so you cant see their abs. Soccer players have smaller and flatter abs, but you can see their 6-pack because they have ZERO fat.
Your abs are muscles SIMILAR to ALL other myscles in your body. For example: Chest, doing bench press with just the bar, this means high reps, will give you a nice and firm chest but not big and bulky. You need to use heavy weigh to do that and it will take MORE time, maybe YEARS.
FIRST OF ALL! Do you want your abs to just look nice and fit? Or do you want your abs to be like huge balls with deep valleys in between?
If you want the first, then do 2-3 sets of crunches and leg raises with no weight every other day.
If you want the second, then use weights. Do plated crunches. Windshield wippers. Any ab exercise that is REALLY hard and you cant do more than 8 reps in the first set. Work heavy and at least for 30' during every ab workout. HOWEVER, this will greatly fatigue your abs, thus you need more rest days, like 3-4. Think logically, you cant dealift, squat, or bench heavy every other day. You are still sore like hell.
Once you understand this basic knowledge YOU will see which exercises you like and you ALONE will create a nice program that fits your goals.
Hope I helped.

Oh and btw, Im speaking from great body building experience here. What I say is what I learned over my years of training.