Yes, I have seen it and I will try to explain the process.
Cut 2, 7 inch dark squares and 2, 7 inch light squares. Put a light square on top of a dark square, right side together. Stitch the left side and the bottom sides together to form a L shaped seam line. Do the same to the other 2 squares.
Grasp the open corners of the dark square and the light square and open up the 2 squares like a birds beak. You will now have a 13 inch larger triangle with one side light and one side dark with a seam line in the center. Do the same to the other square. You can press the seam line or just mark the corner mark to show where you are going to sew from.
Pin the long 13 inch sides of the 2 triangles together one layer only, matching the center seam line and stitch the 13 inch seam. Turn over the square and sew from the corner in until 2 inches away from the seam line. Turn the square around and sew from the corner in until 2 inches from the seam line. Be careful that you are just sewing one layer of each square togther.
You should now have a square with all the seam lines on the outside with a 4 inch unsewn gap in the middle. The gap is how you turn the square right sides out. Turn it and press the square flat.
Your new square should measure approx. 9 inches and you can now cut a square of batt to insert into the square. Once the batt is perfectly flat in the square you can hand sew the gap closed with a hand ladder stitch. The square can be quilted at this point and set aside until you have enough to join them.
I hope you can understand what I have written. I am computer challenged so I can't post pictures. Maybe someone else will know of a site that has a tutorial although this is a very old method.