Pat shrimp completely dry with paper towels. In a large bowl, toss shrimp with salt and pepper, then add ¾ cup cornstarch and toss until evenly coated. Shake off excess.
Heat vegetable oil in a large skillet or wok over medium-high heat until shimmering. Add shrimp in a single layer without overcrowding. Fry for 2-3 minutes per side until golden and crispy. Transfer to a wire rack (not paper towels).
In the same pan, add orange juice, honey, soy sauce, garlic, ginger, orange zest, and red pepper flakes. Bring to a simmer over medium heat and cook for 3-4 minutes, stirring occasionally, until slightly thickened.
Stir cornstarch slurry (1 tablespoon cornstarch mixed with 2 tablespoons water), then drizzle into the sauce while stirring constantly. Sauce will thicken within 30 seconds.
Add crispy shrimp back to the pan and toss gently but quickly to coat every piece with the sticky orange sauce. Garnish with sesame seeds and sliced green onions. Serve immediately over rice or with your favorite sides.