Put water, potatoes, carrots, green onions, green beans, salt, white pepper, and butter in the liner of the Instant Pot.
Put the lid on and turn the pressure to HIGH for 6 minutes. When the cook cycle is complete, perform a quick release.
In a small bowl, combine half and half, flour, and whisk until there are no chunks of flour left.
Turn the Instant Pot to Saute and bring the soup to a simmer. Add the peas and half and half to the simmering soup and cook until it’s slightly thickened, about 5 minutes. Serve and enjoy!