How can I get a six pack or flat stomach?
Visible abs mostly require three things: low-enough body fat, enough abdominal muscle, and genetics that determine where you tend to store fat. Ab exercises can build the muscles, but they do not selectively remove belly fat. "Abs are made in the kitchen, not in the gym." is overstated, but directionally useful: Training can reveal and shape the muscles, but calorie balance is what determines whether enough fat is lost for them to show.
The main levers are a sustainable calorie deficit, enough protein, consistent resistance training, steps or cardio as needed, and patience. Core training still matters for strength, posture, bracing, performance, and appearance, but it cannot replace fat loss. If you want more visible abs, train them like other muscles, recover from that training, and keep the overall diet moving in the right direction.
A flat stomach is also affected by bloating, food volume, posture, menstrual cycle, stress, cortisol, hydration, fiber, and water retention. Do not confuse a normal human abdomen with failure. If the goal becomes obsessive, tied to self-worth, or connected to disordered eating, get appropriate support.