Turn the instant pot on and select sauté.
Add olive oil, onions, celery and garlic.
Sauté them till they become tender and soft.
Add all ingredients except flour and lemon juice.
Lock the lid of the instant pot.
Set the instant pot to “Manual” at high pressure for 10 minutes, release the pressure naturally through steam vent.
Add flour, lemon juice and whisk well.
Add shredded chicken into the soup.
Cook till the soup becomes thick.
Serve hot and season it with salt and pepper.