The method that you have is called Quilt As You Go, or QAYG. I have never done this, so I'm not much help on specifics, but I believe there are several ways of joining your already quilted squares. It comes up on this forum from time to time, so you could try a search here, or search on the internet. I'm sure some of the other members here who have done it will chime in. Good luck.

I sometimes do QAYG, but work with much larger areas than six inches. It would make for a lot of bulky seams that way. If I am making a QAYG I sew as many of the pattern blocks together before I bat and back them to quilt as the machine harp space will allow. One question..........you said some of them are already sewn together with batting and backing. Are there raw seams with all three layers visible on the back? If there are, then this is NOT a QAYG, but shall still need another backing and that's why I'm guessing the brushed nylon is not a backing, but instead more of a batting supplement. It will still need to be backed after the quilt is assembled, and with all that bulk, the intention was likely to tie it.

Yes, there are raw seams on the back from all three layers being sewn together and will need a backing. I'll sew the rest of the blocks together and go from there. I've never seen one put together like this but it should be a nice puffy comforter. Thank you for your advice.