Open the pineapple can, set aside 1/4 cup of juice, the rest will be added to the pressure cooker.
Add all the ingredients from the "Dump & Cook" section to the Instant Pot: chicken, soy sauce, sesame oil, garlic, ginger, hoisin sauce, red pepper flakes, brown sugar and canned pineapple chunks with juice (except the 1/4 cup).
Stir well to combine all the ingredients.
Close lid, make just the pressure cooker is sealed. Select the Poultry function and adjust the time to 5 minutes on High Pressure. Or just select Manual, and select 5 minutes on High Pressure.
Use a 10 minute Natural Release. Turn off the heat. Release the remaining pressure. Open the lid.
Select again the Sauté function, on LOW.
In a small bowl combine 2 tablespoons of cornstarch with 2 tablespoons of pineapple juice, whisk until all combined with no lumps.
Add the mixture to the Instant Pot and gently stir to combine. Cook on Sauté function for a few more minutes, stirring gently, until the sauce thickens.
If you want the sauce even thicker, mix one more tablespoon of cornstarch with 1 tablespoon of juice and add it to the pressure cooker.
Let the chicken stand for 5-7 minutes, the sauce will thicken more.
Serve over rice and garnish with fresh chopped green onions, sesame seeds and slivered almonds.