I agree with fat quarters. Applique the Owls before you put together your quilt sandwich. I'd use stabilzer to make sure they don't pucker. Then I would sew the blocks together in rows, separating each block with a sashing piece and quilt the rows. Leave a couple of inches of backing fabric on each side of the row. Cut the joining strips to be 1/2 inch larger than your finished sashing. Be careful with your 1/4 inch seam allowance and be sure to keep the backing fabric loose. Sew the sashing to one side of the row, right sides together. Press the sashing open. Line up the next row so the top and bottom sashing are aligned right sides together with the sashing piece. Sew together using 1/4 inch seam allowance. Press fully open. Turn under the backing fabric (you might have to trim a little) and hand sew the back seam closed.
Clear as mud right?