A rough picture here (ceiling lights showing on canvas).
As I said before to you, I counted 74 holes in mine instead of the 62 that were indicated on the instructions.
If you have a good look you can see that the Iris itself is pretty much centered inside the diamond shape and to me that was the most important thing to do.
You need to think that you will be stitching your border with a four thread upright gobelin stitch, two over my red line and two under my red line. making the leaves even a bit closer to the border than we see here.
We also need to think about the outside border. We can discuss that a bit later as we still have plenty of stitching to do before we get to this point like stitching the background inside that border, all around the Iris itself.
Let me know if you have problems.