I think its important again to note that although you cannot spot reduce, fat will be burned from all over your body. And the best way to do this is to use as many muscles as possible at every possible opportunity.
This is why I make good use of the plank, as it challenges the many, many muscles within your core, and of course the 'corset' (credit: Gertiegumdrop
)of the lower back and front ab wall.
Id also like to point out that when burning fat is your priority, it will be more efficient to concentrate most of your efforts on using the entire body's muscle groups in order to burn calories.
Exercises such as squats, press ups, and step ups adhere to the principle of using as many muscles as possible, and therefore burn as many calories as possible. Doing these exercises will burn more fat from your stomach area than if you were to simply use core exercises alone.
So the solution? do the total body exercising AND the core exercises. But make the Total Body exercises the priority.