Lactic acid builds up in muscles when all other sources of energy have been exhausted. Some amounts of lactic acid build-up are normal during exercise, but it could be damaging to the muscles or to the body in general to routinely attempt to get to the lactic acid stage in one singled-out area of the body.
Achieving a flat tummy involves many factors. The most important factor being cardio. Lactic acid training anaerobic exercise is the most efficient way to burn the fat off. If all you needed to do for a flat tummy was burn fat off, then we would have found the answer. That is not always the case. Some direct abdominal attention is needed to isolate the region for that final flatness. If you need to lose 2 or more inches off your waist to achieve your goal, then the Anaerobic exercise is the route you want to take.
I do not think that lactic acid training anaerobic exercise is the best way to achieve a flat tummy. I think that if people want to get a flat tummy, people should depend on using aerobic exercises such as running on the treadmill or using the exercise bike. Burning calories is the best way to lose fat.
No I don't believe it will give you a flat tummy. Anaerobic exercise is very good for improving your stamina, endurance, and increasing your lactic acid threshold, but you get a flat tummy by lowering your body fat to a much lower level, and by doing abdominal exercises, and anaerobic exercise makes a minimal contribution to this.
I would have to venture enough to say that most people have no idea what lactic acid training is. Therefore, it can not be the best for achieving a flat tummy. The easiest way to achieve a flat tummy is to get down on the floor and start doing crunches and curls. Simple as that.