For those of us who used to be scribblers and kept paper and pencil/pen almost always, but no more do so because it's a lot easier to write using a computer: Do you use MS Word or Notepad or WordPad? If you are not already using Notepad, then I have a little counsel to give.
Yes, it's to suggest that Notepad would help you reach in a state of flow much faster than MS Word does. It's because of the editing involved while scribbling on MS Word document. You keep on seeing those red lines and editor keeps on pestering with so many suggestions. Yes you're brilliant and know a thousand ways to get a work around this problem. That is perfectly fine, but in case you just wanted to simulate the good-old paper and pen/pencil scribbling-you might try Notepad and you would be surprised with the ease this little change provides.
You would no more get annoying editor suggestions and if you do not use word-wrap then there would be a great width to accommodate a great range of words providing a lot of variables inside your visual periphery, improving the chances of processing all you are writing at once in order to generate greater feedback. The flow attained in the process is very much dependent on speed, therefore getting rid of editor for a while allows you to get a lot of insights and makes writing a lot easier for you. I often forget very simple but useful things which seem like great solutions for many problems and this one is an example of the same. You can always use MS Word to edit what you scribble using Notepad. The white background with good width in Notepad makes it very easy to scribble and you cannot underestimate the importance of writing without an editor. If you keep on doing this for enough long, you would internalize some of the traits of the Word's editor and use more of neurons. If you have done programming then you might remember that masters emphasize coding on Notepad instead of using standard tools like Eclipse (For Java) because of the same reason: Building up a few more associations and engaging few more neurons into the process.