To sew the rows together, I sew together rows 1, 2, and 3. Then I sew row 4 to row 5, then finally the whole thing. I don’t use pins because the nesting seams help keep everything aligned.
Before trimming the patchwork using Template 2 of the Pump Queen pattern, I like to leave this under a heavy book overnight, as this helps the seams stay flat during final assembly.