Can't I say "another foot" instead of "the other foot"?
We generally don't use "another" to describe an action or give directions regarding something with two equal or similar parts, especially in reference to one's body. It sounds a bit awkward and strange. In general, when you are giving directions that require you to complete a double action or manually operate things in two stages, you would use "other" to describe the action. Ex: Put one hand on your head, then reach your other hand around your back. Ex: Hammer the nail into the board, then do the same on the other end.