In a bowl, whisk together the low-sodium soy sauce, brown sugar, ketchup, minced garlic, grated ginger, and sesame oil to create a rich marinade.
Place the chicken thighs in a large bowl or a resealable plastic bag. Pour the marinade over the chicken, ensuring that each piece is well coated. Marinate for at least 30 minutes or ideally a few hours in the refrigerator.
Set your Instant Pot to the 'Sauté' mode. Add the marinated chicken thighs skin-side down and sear for about 3-4 minutes until golden brown. Flip and sear for another 3-4 minutes.
Pour the remaining marinade into the Instant Pot. Seal the lid and set to 'Manual' mode on high pressure for 15 minutes. Allow for a natural release for 10 minutes before performing a quick release.
Remove the chicken thighs and place them on a serving platter. Turn the Instant Pot back to 'Sauté' mode. Mix the cornstarch or arrowroot with a bit of water to create a slurry and stir into the sauce to thicken it.
Drizzle the thickened sauce over the chicken thighs and garnish with sesame seeds and chopped scallions. Serve with steamed rice or noodles.