Prep the potatoes: leave whole any potatoes that are smaller than 3/4-inch in diameter. Halve or quarter larger potatoes into smaller pieces roughly 1-inch in size.
Heat the water: fill a pot with water and place your immersion circulator inside. Set the temperature to 194°F and let the water come up to temperature.
Prep the potatoes: add the potatoes, chives, salt, black pepper, and oil to a gallon-size zip-top freezer bag. Toss together in the bag to distribute the ingredients. Add 3 or 4 heavy soup spoons to the bag—potatoes have a tendency to float, and the spoons will help weigh the bag down. Seal the bag: with as little air as possible, seal the bag, by using the water displacement method to help press out all the air: slowly lower the bag with the potatoes into the water, letting the pressure of the water press the air through the top of the bag. Once the top of the bag reaches the water-line and all the air has been pressed out, seal the bag. Set the potatoes aside on a kitchen towel until the water has finished heating. Cook the potatoes: once the water has come up to temperature, submerge the bag of potatoes in the pot. Make sure the bag is completely submerged; otherwise the potatoes will not cook evenly. Cook for 1 hour, and check for doneness by carefully removing the bag from the water, opening the top and sticking a fork in a potato to determine its tenderness. If not tender all the way through, reseal the bag and continue cooking.
Serve: remove from the water, and turn off the circulator. Transfer to a serving platter and sprinkle some additional fresh chopped herbs and sea salt over the top, if desired. You can also drizzle the cooking oil over the plated potatoes.