Where should the Imam stand while leading the funeral prayer of a female or a male?

Narrated Samura bin Jundab:

I offered the funeral prayer behind the Prophet (ﷺ) for a woman who had died during childbirth and he stood up by the middle of the coffin.

حَدَّثَنَا عِمْرَانُ بْنُ مَيْسَرَةَ، حَدَّثَنَا عَبْدُ الْوَارِثِ، حَدَّثَنَا حُسَيْنٌ، عَنِ ابْنِ بُرَيْدَةَ، حَدَّثَنَا سَمُرَةُ بْنُ جُنْدُبٍ ـ رضى الله عنه ـ قَالَ صَلَّيْتُ وَرَاءَ النَّبِيِّ صلى الله عليه وسلم عَلَى امْرَأَةٍ مَاتَتْ فِي نِفَاسِهَا فَقَامَ عَلَيْهَا وَسَطَهَا‏.‏