Have you worked at free writing before and maybe left it behind? If so, you might want to consider giving it another go. Regardless of where your writing career might be at the moment, free writing can break open any perceived blocks and give you the very basis of an idea that could become your next great story or project.
When I first learned free writing it was as part of a class. It opened a whole new world of insight into how much one could accomplish. Some colleagues will set timers and just go for several minutes and stop right when the clock stops. I know of other colleagues who will give themselves a goal of so many words. They might sprint and shoot for a few thousand before stopping.
It has to be whatever works best for you. There are moments where I will set about free writing and only manage a single word. This is not necessarily representative of an unproductive session. Many times those single words have been revisited later and turned into something bigger and more expansive. They have become freelance pieces, short stories, website content, and blog posts. I’ve managed to make so much of those words work to my advantage.
Writing with the stream of your conscience encourages you to be more open with what you might want to say. It also can perhaps unknowingly give you a sense of self-confidence that may be lacking. Even if you write something without an intention to publish it, it is still writing and therefore still work.
Over the last ten years I have learned that writing can be like a muscle. You can start to lose it and lose focus if you don’t keep working at it. If you find yourself in a lengthy block, keep looking for ways to clear it. Free writing can work for everyone. If you are not sure what to write, then look at another option. Go for a walk and do something physical. Do something that will allow you to engage in free thought. Your mind may pave the road just enough for you to rush to the paper and screen to start fresh again.
Keep at it.