I really admire your flat tummy and body. I would want to achieve that too but you know blogging takes much of our time now that I don't even have time for any exercises again.
I used to do planking, sit ups and leg raise mostly then. In fact, I just started again this morning and I am disciplining myself even if for the next one month to see a good result.
Eating good food is important too as it helps in achieving a good body fitness.
Also, being filled with positive thoughts helps too.
You can do it.. Even just 30 mins of your time.. Do it first thing in the morning since you wake up so early