Preheat oven to 400 degrees. Line a 9x13 inch pan with parchment paper. Alternatively, you can coat with non-stick spray. Arrange the chicken thighs in the pan so that they are close but not touching, skin side down.
In a small bowl, whisk together the water and cornstarch.
In a small saucepan, whisk together the brown sugar, soy sauce, lemon juice, garlic, ginger, and sesame oil. Slowly whisk in cornstarch slurry into the mixture.
Heat teriyaki sauce over medium high heat until it comes to a boil. Reduce heat until it can maintain a gentle boil and allow to cook about 2 minutes until the mixture just starts to thicken. Remove from heat.
Remove about 3 tablespoons of the sauce and reserve for later. Pour remaining sauce over the chicken. Bake in preheated oven for 10-15 minutes or until chicken has reached an internal temperature of 165 degrees F, bake times may vary by thickness and initial temperature of the chicken.
Brush the top of the chicken with the reserved sauce. Garnish with green onion and sesame seeds. Serve with rice or noodles and a steamed vegetable.