I mention QAYG borders for this project in an earlier post.
This is how you do it:
I took the top I had with the middle and triangle borders added, and I quilted it. [I think I will add some more quilting in the white spaces later.]
Then I laid out a three fabric sandwich on the edge where the first border will go.
Top border fabric [black and white check] face-to-face with the top; backing border fabric [green] face-to-face with the back. Pin all three edges together. No batting at this point!
Sew these three layers together. I'm using a quarter-inch seam.
Now take your strip of batting and BUTT it against the edge of the three fabrics you just sewed together. Using a zig-zag stitch sew together, just catching each side without overlaping them.
Here's what it looks like when you are done. This method avoid having two or three layers of the batting on top of each other.
Then you flip the two border fabrics over that seam and press.
Now you quilt this border.
Trim off the excess batting and fabric.
Front has grown by one border side [black and white check].
And the back has grown by one border side [darker green].
Not too tough!
And there are no "covering" strips to add over the seam on either side.
Negative side: You can't rip this border off easily if you later want to change your plan!