In a large bowl, combine the ground beef, breadcrumbs, egg, green onion, garlic, ground ginger, and soy sauce. Form the mixture into golf ball-sized balls.
Turn on the Instant Pot and choose the saute function. Allow the liner to get hot, and add the oil. Working in batches, place a few of the meatballs into the Instant Pot at a time. Brown the meatballs on all sides (about 1-2 minutes per side). Then remove them from the Instant Pot and set aside. Complete the process until all the meatballs have been browned.
Keep the Instant Pot on saute, and pour the water for the sauce into the liner. Deglaze the pot if needed. Use a wooden spoon and scrape off any bits that might be stuck to the bottom. *See notes.
After deglazing the liner, add the soy sauce, garlic powder, ground ginger, brown sugar, and honey. Use a whisk to combine until all the sugar and honey has dissolved. Turn off the Instant Pot.
Place all the meatballs back into the Instant Pot and close the lid. Make sure the valve is set to sealing, and use the manual (pressure cook) button to adjust the time to 5 minutes. After the time is up, turn off the Instant Pot (you don’t want the sauce to stick), and allow a 10 minute natural release before opening the valve for a quick release.
Carefully open the lid and remove the meatballs. Use 1/4 cup of the liquid from the Instant Pot (or 1/4 cup of cold water), and combine it with 2 tablespoons of cornstarch to form a slurry. Whisk until smooth. Turn the Instant Pot to saute, and add the slurry. Whisk to combine and thicken the sauce (whisk for 3-5 minutes).
Turn the Instant Pot off. The meatballs can be added back to the teriyaki sauce or the sauce can be drizzled over the meatballs on a serving platter. Serve with toothpicks as an appetizer or over rice for an entree. Top with sesame seeds and/or sliced green onions.