You don't say how wide the green border is on each block, but it might work to trim it to a half inch all the way around and then add a different color border to make up the difference to your full block size. That way you would have just a quarter inch edging of the green and a more pleasing (to you) wider border on the blocks. No ripping out involved. I would not use ribbon for a flange, nor would I use any flange within a block. They are too difficult to quilt around on the interior parts of a quilt.