Because of its difficulty, it is not recommended for beginners, and it is extremely important to do it correctly. Sloppy or half-baked form won't help your abs, and it just might harm your neck and back. Check out the detailed article about the dragon flag to learn the proper way to do this movement, and a video to learn about progressions before you try it.
I also advise you to take weekly pictures of your body so that you are able to observe how your body changes. You’ll not notice the daily changes solely by looking in the mirror as the changes will be too gradual to be noticed by daily observation but they will be visible when they accumulate. The good thing is that you don’t have to wait until you get six-pack abs to notice major changes in your body. When I was just 5 weeks into my bodyweight training routine, people around me had started complimenting my physique. Seeing your body changing and receiving compliments on your physique will keep you motivated to stay on track.
Go beyond crunches. Sims prefers exercises that challenge you to stabilize your core against imbalance or gravity, like a hands plank with dumbbell pull-through and ab roll-outs using a core-training wheel. "They challenge the entire core by resisting movement instead of creating it," she says of these moves, which she recommends doing in sets of 10 three times. You can repeat the series several times a week.