Add garlic, onion, carrots, celery, rice, vegetable broth, 1 teaspoon fine sea salt, pepper, and herbal spices to the bowl of an Instant Pot or pressure cooker. Pressure cook for 45 minutes then release the pressure by opening the quick release on the top of the lid.
When the Instant Pot has about 5 minutes left to cook, heat olive oil in a small saucepan over medium heat. Whisk in flour and a pinch of sea salt until a paste forms then cook another 1-2 minutes, whisking often. Pour in milk while continuously whisking until you have a smooth sauce. Let simmer about 2 minutes until sauce thickens up a bit.