Its important to remember when you are sewing the rows together, that the seams shouldn't match, they should be offset slightly: this picture just about shows how the far apart the seams are
so there will be a little tail at the end
I make sure that once sewn it will all look ok by using the seam allowance on my ruler
I just hold the ruler in place and then turn the top bit of fabric over to make sure it all lines up - I just do this sitting in front of the machine and if it all lines up, sew it up
Four diamonds make one half
I sewed up my third this afternoon, it takes about an hour I guess.