So you've done some English Paper Piecing over papers
and now you want to quilt it...
To get square edges to add a border,
I tend to just fold over the hexagons
and trim them to a quarter inch to square up the top...
Often it's just two sides that need this folding over and trimming.
Then I take my border strips of fabric and fold over a quarter inch seam on one side.
(You can iron the quarter inch seam if you prefer.)
Sometimes I have done these border strips over paper
and then just sewn them on paper pieced bit to paper pieced bit,
but just folding over is much quicker.
I then pin the border on to the edge of the quilt top...
And just stitch it together.
Hopefully, on the left in the picture below,
you can see the borders being sewn together
(both obviously have quarter inch seams.)
This is the attached border piece from the back:
And from the front:
Now with borders on, you will be able to quilt it!
I used this technique to add the borders on my Rose-Hex quilt.