lilmod ulelamaid # 6 – That is correct. What you wrote is l’chatchila.
If it is hard for whatever reason to remain in place for so long, then at least remain standing in place until the chazzan begins chazaras hashatz. Or, if not that, then wait the amount of time that it takes to walk four amos before stepping back. Which usually you would do anyway if you say the prayer for the rebuilding of the Beis Hamikdash after stepping back.