Construction is of subs is done in several stages but we have no info on just what part of the construction is going to be performed in which hall, to which degree. For example, some US Virginia subs started construction roughly 4 years prior to them being laid down. What laid down means for Virginias is when first two large modules get placed and mated together, forming the basis on which other large sections are joined. Of course, all the big sections are worked on nearly simultaneously through those 4 years.
Now, some work on sections may happen to some degree in a hall separate from those big halls that get most spotlight. But we don't know if all work happens there. It's also likely that, perhaps, empty hull sections get fabricated in separate halls and then transported to the southern halls where all the items, interior construction, subsystems and what not will get placed. And that would likely happen, as with Virginias, pretty much all at the same time, on all sections of the sub.
Basically, if one has a 300 meter long hall, and there is work to be done on all those sections at once, the work process make take up the entire length of the hall, for a single submarine that will in the end be 120 m long. Of course, length of the hall will not be taken up by a single sumbarine and its parts during the entire time that subsections are being worked on and furbished. Once the Sub is largely mated, and there are just months or at best a year before the sub gets launched, there will be a lot of space behind the sub. So first section or two of the next sub will be able to move in behind the completed sub.
Now we don't know if the above is the actual process. It may not be. Maybe sections get fully furbished before they move into the big halls. But in case what was described above is close to the actual process, we'd basically be looking at this: A few years of preconstruction (done in another hall), followed by a few years of joining all the parts within each section (done in the final assembly hall), followed by at most a year of joining those finished sections up and finalizing the sub.
Given that the bigger of the two southern halls seems to have 6 lanes altogether, and that the smaller seems to have 4 lanes planned, that'd suggest a few years per each lane for each sub being built. If we're indeed talking about 10 lanes, and if we're talking, say, 3 years spent in assembly hall, that's roughly 10 submarines launched in said 3 year period. Or approximately 3.6 subs per year. Or approximately one sub launched every 14 weeks.
