Begin by cutting the boneless skinless chicken breasts or tenders into approximately 1-inch pieces. In a shallow dish, coat the chicken pieces thoroughly with cornstarch, ensuring an even layer for a light crust. Set aside as you heat the olive oil in your skillet.

Heat a skillet over medium-high heat and add enough olive oil to coat the bottom. Once the oil is shimmering, add the cornstarch-coated chicken in a single layer. Sauté for about 5-7 minutes, stirring occasionally, until golden brown but not fully cooked.

In a mixing bowl, whisk together the orange marmalade, reduced-sodium soy sauce, white vinegar, sesame oil, ground ginger, minced garlic, and crushed red pepper flakes until well combined.

Transfer the browned chicken to a 6-quart slow cooker and pour the prepared sauce over it. Stir gently to ensure the chicken is evenly coated. Cover the slow cooker and set it to LOW heat, allowing the chicken to cook for 2-3 hours.

Once the cooking time is complete, check that the chicken is tender and cooked through. Garnish with extra sesame seeds and freshly chopped scallions for added texture and freshness. Serve over rice or cauliflower rice.