^^^ this is correct. if you fill in more soil to the point where it is up to the cotyledon leaves ( the small rounded ones) you will be rewarded heavily with a very strong root base. once you fill the dirt up (change containers if you have to(CAREFULLY!)) and the plant is just above the soil where very little stem is visible, then put a small fan blowing directly on it. it must be deep in the soil though! this will provide you with a very thick stem to help make the plant grow faster.