Prepare the frozen crispy chicken strips according to the package directions (air fry 11–12 minutes is recommended). Let them cool until warm, then cut into bite-sized pieces and transfer to a large bowl.
In a medium pot over medium-high heat, add 2 tablespoons toasted sesame oil. When the oil shimmers, add the minced garlic, ginger paste, and red pepper flakes and cook, stirring constantly, for about 30 seconds.
Add the light brown sugar and granulated sugar to the pot and stir to moisten. Stir in the orange juice (and 1–2 teaspoons orange zest if using) until the sugar dissolves.
Stir in the white vinegar and soy sauce, then bring the mixture to a gentle simmer.
In a small bowl whisk the cornstarch with 1/4 cup water until completely smooth, then whisk the slurry into the simmering sauce. Cook, stirring frequently, until the sauce thickens to a syrupy consistency.
Taste the sauce and adjust seasoning if desired (more red pepper flakes for heat or a pinch of salt). Pour as much sauce over the cut chicken as you like and gently toss to coat.
Drizzle the remaining 2 teaspoons toasted sesame oil over the coated chicken, toss lightly, and serve immediately over cooked rice if desired. Garnish with sesame seeds and sliced green onions if you like.