It is recommended to stand to the right of the Imam — Sahih Muslim 709 a

When we prayed behind the Messenger of Allah (ﷺ) we cherished to be on his right side so that his face would turn towards us (at the end of the prayer), and he (the narrator) said: I heard him say: O my Lord! save me from Thy torment on the Day when Thoil, wouldst raise or gather Thy servants.