Oh ,ok. I think I get what you're looking for. If it were me, I'd sew a stip of geese to each side of the block, sew the blocks together in horizontal rows, then sew the rows together. Just like I'd do with any other sashing. The FG are, in effect, just a fancy sashing between the vertical rows, right? I think it would be easier to work with smaller sections of FG between blocks being joined horizontally, than to sew one long one between vertical rows.
Did I understand you right? :)