The Laws of Prayer (The morning services) (22)

1. One who is standing in order to pray the Amidah should align his two feet next to each other as if they were one foot so as to compare himself to the angels about whom the verse says “And their foot is a straight foot”. If one did not do this one has still fulfilled one’s obligation. (Shulchan Aruch and Mishne Berurah 95)

2. Even one who has been forced to sit for the Amidah, should align his feet next to each other. He should not lean back or to one side, nor should he stretch his legs out or cross his legs. He should sit with his head bowed, in a humble manner. (ibid)