Is it permissible to let the hair grow as is the sunnah, but cut it from the back right under the earlobes with scissors. Hair will continue to grow but will be even from the back of the head. I see many people doing this but not sure if this is sunnah or haram as it will result in uneven hair.
In the Name of Allah, the Most Gracious, the Most Merciful.
Assalāmu ῾alaykum wa Rahmatullāhi Wabarakātu
One of the Sunnah ways of keeping the hair is wafrah. That is to keep the hair in line with the earlobes.
One may cut the hair under the earlobes with scissors. The prohibited unevenness of the hair refers to the uneven cutting of the hair on the head where one part is long and the other is short. In the case of wafrah, an even cut of all the hair takes place. 
And Allāh Ta῾āla Knows Best
Student Dārul Iftā
Checked and Approved by:
Mufti Ebrahim Desai