Open the can of pineapple and reserve 1/4 cup of juice; add the remaining pineapple chunks into the Instant Pot.
Add chicken, soy sauce, sesame oil, minced garlic, grated ginger, brown sugar, hoisin sauce, and red pepper flakes to the pot and stir to combine.
Secure the Instant Pot lid and select the Poultry or Manual high pressure setting for 4 minutes.
Let the pressure release naturally for 5 minutes, then manually release any remaining pressure.
In a small bowl, whisk cornstarch with the reserved pineapple juice until smooth.
Stir the cornstarch mixture into the pot, then use the Sauté function on low to thicken the sauce, stirring gently.
Let the dish stand for 5 to 7 minutes before serving over rice or your preferred grain.
Garnish with sliced green onions, sesame seeds, and slivered almonds before serving.