Having A Full Workout Just For Abs. All you need is 15 minutes. If you're already doing compound exercises like squats and deadlifts, one or two ab exercises for 2-3 sets each at the end of your workout is sufficient. You can train your abs all you want, but if your diet isn't in check, you'll never see that six-pack.
The truth is that your abdominals are just like any other muscle in your body. They need some rest in-between exercise bouts as well. Doing some crunches or planks at the end of every workout leaves your midsection in a constantly overworked state, preventing any results you'd like to see.