Step 7: Sew Rows Together
Lay one on top of the other, hem sides out. As far as possible align the egde and stretch/compress as necessary so that there is a good alignment at the corner of four squares. Pin down the whole edge about 5cm in.
Don't stress it too much if you miss by a centimetre or so, it's lost in the overall awesome-ness of the completed blanket.
By the time you get to the last row, you are holding a large row of material while feeding it through the sewing machine, stick with it.