Sorry, trick question - you can't. "Spot reduction" is the attempt to reduce the fat sitting on certain areas of the body. Many of us already know this is a myth yet the tendency to gravitate to "ab" programs and abdominal exercises seems inexorable at times. It's as if there's this little section in our brain which says "despite all the research done so far to disprove spot reduction2,3,4 I feel I need to 'work my abs' to get rid of that last stubborn layer." Like many things what we feel we need to do may not be what we actually need to do. So how can you utilize a fitness program to get rid of belly fat? There's only one way:
Lose body fat. That means lose fat in general. Keeping the amount of calories burned higher than what you take in each day will result in a bodyfat reduction (the "energy equation"). Based on what I've seen over the years, the typical rule is "first on, last off" - the first place you put it on is the last place you will lose it from; it works kind of like a pyramid. This is all genetically determined but regardless of heredity you will reduce your bodyfat percentage if you adhere to the energy equation. When your waistline shrinks in relation to the rest of your body isn't something you can control, but you can control if it shrinks and to some extent how quickly.
So do you need to "work your abs"? If you're on a decently-programmed strength training regimen already then you typically don't need to add anything extra for your middle. Sufficiently-heavy squats, deadlifts, chinups, etc. all make your abdominals contract very intensely in ways that sit-ups & crunches don't do, and in ways that your body is meant to function. Planks, Chops and Pallof Presses can help you learn how to feel your midsection contracting so you can actively tense up those muscles when doing bigger movements; and for beginner exercisers getting those muscles re-engaged is a big help in developing stability.
In short, if you want to slim your waistline burn more calories than you consume. "Ab routines" might make you sore at first, but there is no demonstrable crossover from sore abs to belly fat reduction.
2 Effects of Sit up Exercise Training on Adipose Cell Size and Adiposity, Katch et al, 1983
3 The effect of abdominal exercise on abdominal fat, J Strength Cond Res., 2011
4 Regional fat changes induced by localized muscle endurance resistance training, J Strength Cond Res., 2013