In a saucepan, combine the vinegar, sugar, water, red chili flakes, salt, and chopped garlic. Bring the mixture to a boil over medium heat, then reduce the heat and let it simmer for 4–5 minutes to allow the flavors to blend. Next, add the cornflour slurry (cornflour dissolved in 10 ml of water) and stir continuously until the sauce thickens slightly, about 1–2 minutes. Remove from heat and let it cool completely. Once cooled, transfer the sauce to a clean jar and refrigerate. Enjoy this spicy and tangy chilli garlic sauce as a dip, drizzle, or a flavor booster in your favorite dishes!