But basically: if you want less fat flab, eat and drink less calories (so drink more water) and/or be more active. There's no way to target specific areas to reduce fat.
It's going to take you time to accept the feeling of being slightly hungry, it's going to take time for you to adjust to different eating and (water) drinking habits, and time to adjust how much you dedicate to activity (be it formal exercise or something that get you moving). It's a lifelong habit change if you're serious about maintaining a look or just physical health, and it's all going to take time.
(If you do formal exercise, lean toward strength. Starting out, both cardio and strength are effectively both. But having some muscle burns more calories. Strength also can be done more readily than cardio; set of bodyweight squats after pee for example. Remember, it takes time for your stabilizer muscles to develop, on top of your targeted muscles. And they build while you're recovering and resting from workout.)
The slower you go/ make changes, the more likely the habit sticks. Because it's "easy". Power to you if you can do the recommended safe 1-2 pounds a week (about 500 to 1000 calories deficit a day), and immediately dedicating 2.5 hours+ of your week to exercise. I couldn't, and I rebounded to be even worse.
For my experience, going much slower, I can maintain smaller meals/ less calories easily some 4 years later (from about 2400-2500 daily calories to 1600-1700, or decreasing my calorie intake by about 150-200 a year on average). Currently trying to gain muscle and am quite active (found and made time for 2-3 hours exercise a week since i started wanting to do it around 2nd or 3rd year), so increased protein intake and back to 1900-2000 daily calories for now.
Note 1: if you're under 20 years old and in your growing phase, do not deprive yourself of nutrition and calories; your body needs it to grow. Unless you know you eat only "junk" and are very overweight/obese, lower your intake a small amount if you insist. Ideally just be more active and possibly eat a bit better.
Note 2: And if you primarily eat junk, have a look at a basic daily multivitamin supplement from like Costco. Won't do anything noticeable immediately, but when your body knows it at least has some nutritients to work with, it can maintain itself better.