Set the Instant Pot to saute and add the olive oil. Gently cook the onion, carrot and celery until softened. Stir frequently. Add the garlic, cumin, salt, pepper and thyme, cook for one minute.
Add the vegetable stock, lentils, tomato puree and bay leaf. Stir well. Place the lid on the pot and make sure the valve is in the "sealing" position. Cook on manual for 30 minutes.
Use natural pressure release, it may take 15-20 minutes until the lid can be released.
Serve with some crusty bread or just a drizzle of olive oil.