Press saute button in Instant Pot and allow pot to become hot. While doing so, dice green pepper, onions and garlic.
Once pot reads hot, add 1 TBS oil and ground beef to pan. Break apart and allow to brown. After about 2 minutes, add in green pepper and onions and saute all for about 5 minutes. After 5 minutes, add garlic and saute additional minute.
Push cancel on Instant Pot. Make sure nothing is stuck to the bottom of the pot.
Add additional ingredients to pot; water, ketchup, light brown sugar, chili powder, dry mustard, Worcestershire sauce, salt, pepper and red pepper flakes. Stir all ingredients together.
Put lid on pot and seal valve. Press manual/pressure cook and adjust the time to 8 minutes.
When timer goes off, allow pressure to naturally release for about 5 minutes then you can release all remaining pressure.
Open pot and press saute. Allow sauce to thicken before serving. This will take about 5 minutes.
Serve on buns or for a low carb option, try a portabella mushroom.