Grab the Instant Pot and hit the saute button for 5 minutes on high. Add the butter and the flour and stir with a wooden spoon until it's melted and mixed.
Pour in the chicken broth and stir.
Add the salt and pepper. Stir.
Let it simmer for a short while so that it thickens.
Video
Notes
If the gravy is too thin, you can easily thicken it up by adding in a small amount of cornstarch. Just add, stir, let it simmer, and then serve or add some more to thicken it even more.
Make sure that you're stirring the flour when it's in the Instant Pot as you don't want it to burn. Use a wooden spoon to stir so that you don't scrape up the inner pot.