When two people pray together as a congregation, the imam and the person following him should stand level, side by side. The imam should not be further forward, whether by a little or a lot, because they constitute one ṣaff (row) and the sunnah is for the ṣaff to be straight and level. [Ṣifat Al Ṣalāt by Sheikh Al ‘Uthaymīn p.205].