I have attached the recent paper published on 28th September 2018, "Glassy Carbon: A Promising Material for Micro and Nanomanufacturing" which will help you.
I would like to thank the colleagues who spent their time and supplied us with links of good papers covering the topic glassy carbon.
It seems that glassy carbon is polycrysatlline graphite that can be extracted by pyrolysis of polymer which is heating of polymer under oxygen free ambient till the formation of glassy carbon. The conditions of the reaction for different polymers are given in the paper brought by Samir.