In a small pot, combine the garlic, ginger, rice vinegar, ⅓ cup water, sugar, sambal oelek, red chili flakes, and soy sauce. Bring heat to medium, and let it cook for 5 minutes, stirring frequently.
In a small bowl, combine the cornstarch and 1 tablespoon of water. Whisk to remove any lumps, then add this mixture to the pot on the stove.
Reduce heat to low and cook the sauce for about 10 minutes, or until the sauce has thickened. Once thickened, remove from the heat to cool. Store in a glass jar, or serve right away.