Turn the Instant Pot on to the sauté function. Add olive oil, onion, carrots and celery. Cook, stirring frequently for a few minutes, until the onion begins to turn translucent.
Add garlic, thyme, bay leaves, salt and pepper. Stir again and cook for an additional minute.
Place ham hock in the pot, add chicken stock and split peas.
Give it another stir, then place lid on and lock into position. Set steam lever to "sealing" position on top of the lid.
Cancel "saute" function and select "manual". Set to 20 minutes (using the +/- buttons).
When the timer goes off, let the pot naturally release for 10 - 12 minutes, then you can move the lever to venting to carefully release some of the steam.
Open the lid, remove the ham hock and the bay leaves. Discard them.
Stir soup and serve as is or with browned diced ham on top.