Are you wanting to seam it where it's pinned now? What if you pressed the top layer where you have it folded? Then mark the bottom layer with a disappearing pen, or bast along that line. Then you can lay the fabric right sides together, and match the ironed fold with the pen marks/basting line. Pin well. I think it will be very difficult to get it exact.
Or --- are you matching two lengths of the fabric? Can you determine how many inches in from the salvage one fabric needs to be to make the match? Also, it looks like you might have a few points that you can match. The edge of the hexagon with the leaves looks like it should match, as well as the squares in the gingham section. I've never used a glue as someone suggested in a previous post, but that might work, or use pins. Reminds me of matching plaids when sewing.
If I'm not understanding your problem, just ignore my ramblings.
Good Luck