Maybe you'll be gifted some advice to the effect of 'ignore all this crap, just do this, then that, and you'll have it'. I'm just not to that level.
As I mentioned before
@jbogard, I might need to graft to get a branch where I would like one to be. A thread graft requires a long shoot that can be bent around in a loop that intersects the trunk. So, I will explore whether I get shoots next year that will be long enough to do this. If there is, I might proceed with creating a thread graft before fall and after removing the leaves on it. If I don't get one suitable long shoot, I would need a separate sapling on its own roots to be the thread. Prospectively, now that I think about it, I might have tried to root cuttings (aha! the stuff exploratively cut off spring 2020) to be that sapling on its own roots. That might not be easily done so maybe I punt on this notion and accept that I'm trying to put a square peg into a round hole meaning this tree really ought to be made into a different image. Nevertheless, I will have learned a few things and will not have done anything to impair the health of this tree
You also need to work on getting it out of the nursery soil and into an inorganic substrate, and you need to clearly see the nebari. I've repotted cork oaks in spring (about the time old leaves start to drop) and after the summer solstice, around Aug/Sep. Either time works well. I am reasonably certain that live oaks will cope similarly, so choose your poison, so to speak. I also haven't had any trouble with bare rooting cork oaks in the process, but you may want to be more prudent and only remove the nursery soil from the roots on one side of the trunk (HBR =
half
bare
root) placing it in a container of inorganic substrate and then finish the job late in the summer or in spring 2021.
That is a lot of stuff to do next year (2020). Maybe it is very unsatisfying for you, in the sense that almost nothing has been done toward styling this tree. I can also imagine other images that are maybe better suited to your tree. The classic oak image is a thick stout trunk with long wandering heavy branches that are so heavy that they sometimes rest on the ground. Your tree's trunk is far to tall for this. Of course, you could also choose to make the image of a younger oak. Still the trunk seems too tall to me - that is the core problem for me. A literati-like image wouldn't require doing anything that effectively shortens that trunk, but it would become a rather arty thing that honestly doesn't interest me. So, I'm stuck in my thinking right now - I keep coming back to need to shorten the tree somehow.
Maybe if the trunk was slanted instead of going straight up out of the ground, it wouldn't be such a problem. I've seen many trees that seem to arc up out of the ground. This might be cool if this tree has a really crappy nebari and doesn't flare. Trees I see like this almost always smoothly bend upward from almost parallel to the ground and the vertical end of the trunk tends to look very much like an ordinary tree. Even though this is a common juniper/pine image, it may be a sensible solution for your tree and one of those two lowest branches becomes the vertical part of the trunk. You will be creating that top over time, wiring and clip and growing to make the trunk top and all its branches 'bend to your will'. This, of course, you basically will have already learned to do, next year.
You see, I'm also a rank amateur, not certain what kind of tree I would eventually have. But I have a list of things to do in 2020 and some questions that I can possibly answer by observing, imagining, and thinking in the meantime. I've done lots of things that turned out to be stupid in hind sight. I've still got most of my original trees. Many were butt-ugly and hopeless, but they are healthy. So, I've started them anew (in a sense) and am doing something different with them. I now better understand what it takes to make a decent bonsai that I did back then. I keep my trees healthy and I keep trying to make them into decent bonsai. Yes, I've killed a few.
Find a vision, make a plan and decide what you'll need to know and be able to do to pull it off. Try it and rethink when it doesn't work out. Try again. Aside from an enjoyable and entertaining waste of my time, this is what I've gotten from my roughly decade's worth of experience. This and two or three trees my wife doesn't call "cute".
... just sharing, though I am fully aware, belaboring the point.