Set the pot on sauté mode and fry the bacon until it is crisp. Remove and reserve bacon bits. Add the celery and the onions to the pot and sauté for around 2 - 3 minutes, stirring constantly. Add the flour to the pot and mix in well. Add the clam juice (not the clams), thyme, chopped celery leaves and the potatoes into the pot. Stir it up to mix well. Secure the lid and close the pressure valve. Cancel the sauté mode and set the pot manually for high pressure and 5 minutes. Press start. When it is done do a quick release. Push the cancel button and set the pot to sauté again. Push start. Add in the clams, cream, salt and the pepper. Bring to a simmer while stirring. Simmer for about 2 more minutes, while stirring. Taste and season as necessary. Cancel the sauté mode and set the pot to keep warm. Serve hot with bacon, oyster crackers and a pat of butter on top.