Preheat oven to 400°F and line a large sheet pan with parchment paper.
Whisk together soy sauce, orange juice, water, honey, minced garlic, minced ginger, chili flakes, lemon juice, and gluten-free flour in a small saucepan until smooth.
Simmer over medium heat, stirring occasionally, for 5–7 minutes until the glaze thickens enough to coat the back of a spoon.
Pat salmon fillets completely dry and arrange on the prepared sheet pan, spacing them evenly.
Brush each fillet generously with the teriyaki glaze, reserving about 1/4 cup for finishing after baking.
Bake for 12–15 minutes, checking at 12 minutes; the internal temperature should reach exactly 145°F in the thickest part.
Remove from the oven and let the salmon cool for 15 minutes at room temperature for proper storage.
Portion salmon into glass meal prep containers, brush with remaining glaze, and top with sliced green onions and sesame seeds.
Optional for complete meals: Add cooked broccoli florets and brown rice (or cauliflower rice) in separate compartments for easy reheating.