Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Dice the chicken breast into uniform 1-inch cubes and place them in a mixing bowl.
In a small saucepan over medium heat, whisk together the orange juice, tamari, honey, grated ginger, minced garlic, arrowroot powder, and red pepper flakes.
Simmer the sauce for 3-4 minutes, stirring constantly until it thickens into a glossy glaze that coats the back of a spoon.
Toss the chicken cubes with half of the prepared orange glaze until well coated, then spread them onto one side of the baking sheet.
Place the broccoli florets on the other side of the baking sheet and drizzle them with the sesame oil.
Bake for 15 to 18 minutes, or until the chicken is cooked through and the broccoli is vibrant with slightly charred edges.
Arrange the warm brown rice in a bowl, top with the baked chicken and broccoli, drizzle with the remaining orange glaze, and garnish with sesame seeds.