Try searching the forum, there are several threads with roughly the same question..
In short, you need something to support the entire oven, people usually cast a slab of pure concrete. Then you need something to insulate between the slab and the firebrick, you can use various materials, the simplest (best and most expensive) is to use a fire protection board (I bought one called "skamotec" something), but you can use vermiculite, leca, or even empty glass bottles and sand...
I don't quite understand what you mean by "rotating rod," I assume you mean the temporary support you can use when building the dome... The idea is that it should be the same length all the time, but I think it's much easier to either fill up with sand and build against it, or build a wooden plug that you burn out when you're done (and the oven has completely dried out for a few weeks with a small heat source in)...