Stir the riced cauliflower, coconut milk, and sea salt together in the Instant Pot insert until combined.
Seal the lid and set the manual cook time to 1 minute. When the timer elapses, immediately release the pressure and remove the lid once the pressure is fully released. There should only be a very small amount of liquid remaining and the large majority of the liquid should have been absorbed by the cauliflower rice.
Sprinkle the arrowroot starch on top of the cauliflower rice and stir until thickened. There should not be any liquid remaining in the pot at this point. Immediately transfer to a serving dish and serve warm.