Your blocks look like mine did when I made my OBW, except I trimmed all my dog ears off. All my seams were pressed open and I sewed mine in strips so there were no set-in seams. I just lined up my center seams when putting the rows together. You do need to lay the whole quilt out so when you put your rows of three together you keep the halves of the block together. I used black as an inner border (it was in my material) and then used the material I used in the center for the outer border. Actually, they don't need borders, but then you need to run a seam around the outside to keep the blocks from coming apart when it is being quilted. Turned out great! Yours will be lovely!!!