We write the best way, not when trying to perfect every sentence as we write our first draft, but when writing down our thoughts and not revising them till we finish that draft. Now in some books I have read, the authors advises their readers to use free writing to come up with material for their works. But I cannot imagine myself to use free writing, because it is not easy for me to write without stopping. I think I need to write more slowly, setting down only those thoughts that are meaningful, and revising those thoughts that are not what I intended them to be, not to make them clear or graceful, but to make their meaning precise.
I shall go against the flow and say that some people do not work well with free-writing.
Ggiaquin does a great job explaining why it is a helpful technique and, especially when trying to get over a writer's block, I'd quickly suggest it.
However, I understand the OP's point. My writing is very much driven by the character's emotional state (whether they're cool headed or in the throes of melodrama). The narrator's voice must always strike the right voice. If, for some reason, the sentences come off slightly out of character or if the emotion conveyed isn't quite right, then that is an equivalent to someone interruptiong me. It kills the flow.
What I do, in order to get the right voice in my head so the writing flows quickly and in character and also in order to get the right emotion, is to stop writing and to play the scene in my head a number of times. I go over the emotion, the actions, the words. I become the main character of the scene and repeat it over and over (doing so while doing a completely physical activity, like vacuuming, can help). Then I get inside the other characters and make sure their actions and reactions are also in character. Finally I can sit down and write because the voices and the emotions are just right. I have written over five thousand words in a sitting after doing this preparation. The later editing comes down much more to just spelling and getting a few synonyms, because the events and the emotions usually come out right from the start.
In a way, it's also a form or free writing in ggiaqin's sense - it allows to write without being interrupted, whether by your inner editor or by a feeling that something is off which kills your progression. Just prepare yourself until you've got the right tone for your thoughts. Or perhaps just go over your thoughts without writing them in order to improve them, to help them evolve into the right idea. Once you feel the right idea booming inside you, you'll be able to write non-stop, fed by that feeling.
You are still missing the point of free writing and many of our suggestions in your previous questions. The whole point of free writing is not to kill your flow. Think of it this way... you are watching a movie... someone comes in and talks to you so you pause it. Play it for another 5 minutes, someone else comes in and talks to you so you pause it. Then you play again. Again someone interrupts you and you got to pause the movie again. You can't enjoy the flow and pacing of the movie if you are having to pause it every 10 minutes. You also have to spend time trying to remember where even you left off and what just happened.
I understand you want to slow yourself down. This still causes the main issue of stopping yourself after every sentence. Free writing does not necessarily mean you rush through your writing with every first thought in your head. It simply means that you allow yourself to turn off the editor/revision mode in your mind and allow thoughts to be put to paper without critique. You can do this as fast or slow as you want, but the key is to not allow yourself to go back and edit or think if the sentence needs to be changed before writing.
That seems to be your biggest struggle because you want to control and force your words a certain way. It is hard to build rhythm and flow and elegance if you are trying to take your foot and jam it in. That's what it feels like you are trying to do to me. You need to let go and relax and stop looking for perfection with your first try.
I feel like, in your situation based on the questions you have asked, you would really benefit from free-writing and it should not be avoided. Especially if you want to learn how to build rhythm.
It's like playing an instrument. Just let it flow man, if you make a mistake keep going, you don't see musicians stop if they make a mistake. Often it is hard to hear mistakes when it is live because they keep the flow going. Imagine if you were listening to a live concert and every time someone in the band messed up, they would stop and redo the song. Concerts would be the whole day. Some times, you need to look past the minor mistakes, the minor issues, to build the overall flow and then go back and change the couple of words you feel are out of place.
For most, that sort of deliberation is best done later, in edits or second drafts. However, if you'd like a way to force yourself to maintain a slower pace and think over words more before the first time you write them down, I've found that writing by hand is very valuable for that. It slows down the pace of your writing so that your mind can think of more different permutations of the words you have yet to write down.
There is story development and there is narration. You need to compose a story before you can narrate it. Some people are naturals at story development. For them the story flows so naturally that they can focus on narration from the moment they start writing.
Some people struggle with story development. Some address this with planning and outlines. Some do the story development in their heads before they start narrating. And some start scribbling down whatever comes into their heads and hope a story thread will emerge from it. This is what so called free writing is about.
Some people are naturals at narration. For them, the narrative flow emerges more or less intact in the first draft. For others, constructing a working narrative is a laborious process of many revisions. Don't expect your free writing story development to produce a great narrative. And don't confuse that process with the behavior of people who are both naturals at story and naturals at narration and can get a good first draft done first time out.
If free writing is your method for story generation, then don't worry about the writing details because this is not you first draft of the narrative, it is merely story generation. Be prepared (indeed, work with the full intention) to throw the entire thing away once you have found your story shape, and then begin the task of narration over from the beginning.