Pat the chicken thighs dry with paper towels and season with salt and pepper. Dust them lightly on both sides with rice flour, shaking off the excess.
Heat the vegetable oil in a large skillet over medium-high heat. Place the chicken thighs in the pan and cook without moving for 5 to 6 minutes, until the underside is deeply golden and crispy. Flip and cook for another 4 to 5 minutes until cooked through and golden on both sides. Transfer the chicken to a plate.
While the chicken cooks, whisk together the tamari, mirin, honey, rice vinegar, garlic, and ginger in a small bowl. In a separate tiny bowl, stir together the cornstarch and water to make a slurry.
Reduce the heat to medium and pour the teriyaki sauce into the same skillet. Let it simmer for about 1 minute, scraping up any browned bits from the bottom. Stir in the cornstarch slurry and cook for another 30 seconds to 1 minute until the sauce thickens and becomes glossy.
Return the chicken to the skillet and flip it several times so every piece is coated in the thick, sticky sauce. Let it simmer together for about 1 minute so the flavors meld.
Transfer to a serving plate and spoon any remaining sauce from the pan over the chicken. Garnish with sesame seeds and sliced green onions. Serve over steamed rice.