Press Sauté; heat oil in Instant Pot®. Add onion; cook and stir 3 minutes or until softened. Add jalapeño, garlic, chili powder, salt, cumin, oregano, black pepper and red pepper flakes, if desired; cook and stir 30 seconds. Stir in broth; cook 1 minute. Add chicken, hominy and beans; mix well.
Secure lid and move pressure release valve to Sealing position. Press Manual or Pressure Cook; cook at high pressure 6 minutes.
When cooking is complete, use natural release for 10 minutes, then release remaining pressure.
For thicker chili, stir 1 tablespoon flour into 3 tablespoons cooking liquid in small bowl until smooth. Press Sauté; add flour mixture to chili. Cook about 5 minutes or until chili thickens, stirring occasionally. Garnish withcilantro.