Once you’re ready to cook the potstickers, heat two tablespoons of neutral oil over medium-high heat in a nonstick skillet or pot that has a tight-fitting lid. Arrange them in an even layer, separating into batches so that they’re not crowded. Stand each one filling-side down, with the connected edges pointing up. Fry them until the bottoms just start to brown — about a minute — then add 2/3 of a cup of water, being careful of spatters from the hot skillet. Cover the skillet and cook until tender, about six minutes.