In any pickle you should never be behind the bag. we teach fielders to be inside diamond and not in base-line/base-path. Give the runner the base-path so you don't obstruct them and also so you are not throwing the ball over the runner. If you are behind the bag the runner can get her foot in before you apply the tag. Inside the base path and a step or 2 before the bag is good position.
Sorry, the "stand behind the bag" was sarcasm. Of course we'd never teach that.