Cut chicken into 1-inch cubes and coat with cornstarch, salt, and pepper.
In a bowl, whisk together honey, soy sauce, water, minced garlic, rice vinegar, sesame oil, red pepper flakes (if using), and cornstarch to prepare the sauce.
Heat olive oil in a skillet over medium-high heat; cook the chicken until golden brown and cooked through.
Pour the honey garlic sauce into the skillet; let it simmer until thickened.
Combine chicken with the sauce to ensure even coating and serve immediately over rice or quinoa.