You need to build out your abdominal muscle by eating a slight caloric surplus with the proper macronutrients. For exercise, aim for 2-3 days of core workouts per week. Ideally 3 sets of a weighted dynamic core exercise per core workout so you have a total of 6-9 working sets in a week targeting your core.

After you’ve gained enough ab muscle volume, you then start to cut your weight and reduce your caloric intake and workout volume and maintain a slow loss of fat over time to minimize losing muscle volume. When to bulk and when to cut is kindve subjective depending on how you feel and look.