The best approach to writing an original character is to write a story. Once you have wrote up that story for the character and it's family, from there, continue writing that story throughout your time roleplaying as them. You don't need to particularly fact-file a character (personally, I find fact-filing a difficult thing to do when it comes to characters which is why I haven't posted any biographies on 'recent' characters). This is the most unique and abstract way of going around it if making a biography is not the type of thing you like doing.
In short, consider your story opening and character introduction, and then complete the rest of your story mountain on SRP. Feel free to document your biography whenever after the opening. Take your time with it + don't rush yourself most of all! It all takes time.