Look, you may hate crunches with a passion, but a good routine should take no more than ten minutes and day and will be very effective. My routine:
1. Regular crunches (slow set of 4, fast set of 16)
2. Touch elbow to opposite knee (slow set of 4, switch sides, fast set of 16, switch sides)
3. Side crunches -- shoulders off the floor, touch your hand to your ankle on the same side (slow set of 4, switch sides, fast set of 16, switch sides)
4. Leg lifts -- one foot on the floor, lift straight leg up to 45 degrees while crunching (slow set of 4, switch sides, fast set of 16, switch sides)
5. Peddling -- shoulders off the floor, bring one knee in while extending other leg straight out in peddling motion (set of 16)
6. Reverse Peddling -- same thing, reverse direction (set of 16)
7. Scissors -- shoulders off the floor, legs lifted slightly off the floor, bring one leg up to 45 degrees, switch legs in a "scissor" motion, do not touch legs or shoulders to floor (slow set of 4, fast set of 16)
I do this daily and switch it up or make it more complicated with other pilates exercises to keep from getting bored. The most important thing is to keep your back from arching -- keep it flat on the floor at all times. If you're just starting a routine and this is too much, do what you can and rest a day between routines. As you get stronger, it will get easier. If it's too easy, add more reps.
After the routine, turn to lay on your stomach and then push up on your hands to arch your back and stretch out your abs. Relax down and then stretch up again, repeating a couple of time and trying to arch higher and stretch more each time. Stretching is always important.