Prepare the celery, carrots, onion, and potatoes.
Rinse the lentils and remove any stems.
Press the Instant Pot “Sauté” button, medium setting.
After the Instant Pot comes to temperature, add olive oil celery, carrots, and onion and sauté until vegetables soften a little, 5-7 minutes.
Press the Cancel button.
Add the potatoes, lentils and the thyme bundle.
Add salt, pepper, cumin, and red pepper flakes (optional).
Add vegetable broth.
Cook on manual for 7 minutes, followed by quick pressure release.
Open the lid and stir in the spinach.
Serve over rice, if desired, with crusty bread and perhaps a light salad.