Step 1: Lay out your blocks
Step 2: Cut your sashing/border:
Cut 17, 10 1/2" x 2 1/2" strips
Cut 5 strips 2 1/2" x width of fabric
Cut 6 cornerstones, 2 1/2" squares
So I straightened them up with my rotary cutter before assembling my rows:
Step 6: Sew the rows together.
Step 7: Borders. You will use your width-of-fabric strips for the borders. Cut off the selvedges from two of the strips and piece them together. Then press that seam and sew the border to one of your long sides. Cut off the excess--I cut about 1/2" beyond the quilt top edge with my scissors and then go back and trim with the rotary cutter after pressing the border piece.
Then make sure you have a straight edge on your short piece and repeat for the other long side. Press and trim the border pieces on the long sides.
Sew the remaining border pieces to the short sides of your quilt, trim the edges and you're done with the quilt top!