In a saucepan, combine sugar, water, and rice vinegar over medium heat.
Stir until the sugar is completely dissolved.
Add the minced garlic and chili flakes to the mixture.
Bring the mixture to a gentle boil, then reduce the heat.
Let it simmer for about 5 minutes, stirring occasionally.
In a small bowl, mix the cornstarch with 2 tablespoons of water to create a slurry.
Slowly add this slurry to the saucepan, stirring continuously.
Allow the sauce to thicken, about 2-3 minutes.
Remove from heat and stir in the soy sauce and salt.
Let it cool before transferring to a bottle or jar for storage.