Place the Instant Pot on the Sauté function. Add the olive oil and garlic.
Cook until the garlic becomes fragrant.
Add the water, green beans, and cream of mushroom soup (in that order. Do not stir). Add salt and pepper to taste.
Close the pot, lock lid in place, and seal vent in closed position. Cook in Manual High-Pressure Cooking for 14 minutes.
Once your Instant Pot is done, quick release the steam. Turn the Instant Pot to the sauté function
Combine the flour and water in a small bowl to create a slurry, and then add to pot.
Add half of the shredded cheese and gently stir. Cook for a minute or two until the cheese has melted. Then add 1/2 cup fried onions, and gently stir.
Preheat oven to 400°F.
Spray a baking dish with a non-stick cooking spray. Transfer the green bean casserole from Instant Pot to a baking dish. Top with the remaining shredded cheese, panko breadcrumbs, and fried onions.
Bake for 5-7 minutes until the cheese has melted and crisped slightly on top. Allow to cool 5-10 minutes before serving.