In a small bowl, whisk together the soy sauce, rice vinegar, honey, ginger, garlic, sesame oil, green onion, and red pepper flakes (if using) until well combined.
Taste the sauce and adjust the seasoning as needed. If it's too salty, add a bit more honey or rice vinegar. If it's too sweet, add a bit more soy sauce.
Let the sauce sit at room temperature for at least 15-20 minutes to allow the flavors to meld together.
Serve the Soy-Ginger Sauce with your favorite dish, such as grilled chicken, beef, tofu, or vegetables. Enjoy!