You have mentioned that dhikr is an optional prayer and it can be done in any method without having proof from sunnah

 You have mentioned that dhikr is an optional prayer and it can be done in any method without having proof from sunnah. But what about the hadith that Abdullah ibn masood prohibiting some people from making zikr in their own way?

A famous scholars mentions the following:

"A report narrated by al-Tirmidhi (204) from ‘Amr ibn Salamah who said: We were sitting at the door of ‘Abd-Allaah ibn Mas’ood before Fajr prayer, when he came out. We walked with him to the mosque, then Abu Moosa al-Ash’ari came to us and said: Has Abu ‘Abd al-Rahmaan come out to you yet? We said: No. So he sat with us until he came out, and when he came out we all stood up. Abu Moosa said to him: O Abu ‘Abd al-Rahmaan, just now I saw something in the mosque that I have never seen before, but I do not think it was anything but good. He said: What was it? He said: If you live, you will see it. He said: In the mosque I saw some people sitting in circles waiting for the prayer. In every circle there was a man, and in their hands they had pebbles. He would say: Say Allaahu akbar (Allaah is Most Great) one hundred times, and they would say Allaahu akbar one hundred times. He would say: Say Laa ilaaha ill-Allaah (there is no god but Allaah) one hundred times, and they would say Laa ilaaha ill-Allaah one hundred times. He would say:  Say Subhaan-Allaah (Glory be to Allaah) one hundred times, and they would say Subhaan-Allaah one hundred times. He said: What did you say to them? He said: I did not say anything to them; I was waiting to see what you think and I waited for your command. He said: Why did you not tell them to count their bad deeds and guarantee to them that their good deeds would not be wasted? Then he moved on and we moved on with him until he came to one of those circles, and he stood over them and said: What is this that I see you doing? They said: O Abu ‘Abd al-Rahmaan, these are stones with which we count the takbeers (‘Allaahu akbar’), tahleel (‘Laa ilaaha illa-Allaah’) and tasbeeh (‘Subhaan-Allaah’). He said: Count your bad deeds, for I guarantee to you that none of your good deeds will be lost. Woe to you, O ummah of Muhammad! How quickly you have become doomed! His companions are still alive and his cloak has not worn out, and his vessel is not yet broken. By the One in Whose hand is my soul, you are either following a way that is more guided that the way of Muhammad or you are opening the door to misguidance. They said: By Allaah, O Abu ‘Abd al-Rahmaan, we intended nothing but good. He said: How many of those who intended good did not achieve it. The Messenger of Allaah (peace and blessings of Allaah be upon him) told us that some people would recite the Qur’aan and it would not go any further than their collarbones. By Allaah, I do not know, perhaps most of them are from among you. Then he turned away from them and ‘Amr ibn Salamah said: I saw most of those circles on the side of the Khawaarij fighting us on the day of al-Nahrawaan. 

Think about this attitude of Abu Moosa and ‘Abd-Allaah ibn Mas’ood, and how they denounced this method which was not done by the Prophet (peace and blessings of Allaah be upon him) or his companions, although dhikr is basically prescribed, praiseworthy and encouraged. 

The scholars pointed out that doing an act of worship at a specific time or in a specific place, or in a specific manner, that has not been narrated, is regarded as innovation. In that case it is called bid’ah idaafiyyah (an innovation by adding to something that is basically prescribed). It is prescribed in principle but is rejected because of the way in which it is done. "

So i would like to know your answer to this explanation. Jazakallah khairun.