Place the potatoes, water, and salt in the Instant Pot. Make sure the potatoes are completely covered, you can add more water if needed. Place the lid on the instant pot and cook on STEAM for 12 minutes. When finished cooking, carefully quick-release the steam, drain the potatoes and then place the pot back into the Instant Pot. Be careful, it's hot!
While the potatoes are cooking, melt the butter in a small saucepan over medium heat. Once melted, add the garlic thyme, rosemary, and sage and cook for 15 minutes over low-medium heat. Remove the butter from the heat and remove the herbs and garlic.
Keep the Instant Pot on warm and mash the cooked potatoes with your masher. I like my potatoes a little chunky but you can mash as much as you would like. Add the sour cream and herb butter and stir in with a rubber spatula or large spoon. Add salt to taste.