You start by cutting squares of whatever color you want for the "background." Here it is white.
This particular quilt is going to be gigantic, so there are over 700 4-1/2" white squares. The baby quilt (above had squares that started about 4"). Next, you need to cut some triangles, or use scraps. The quilt I am making now is blue and white, so lots and lots of blue triangles.
Then sew the triangles to the squares.
You have to make sure that when you fold it over, the colored piece covers the white square.
Then you trim. This part is tedious. I suggest "watching" TV at the same time.
Next you trim away the excess BACKGROUND fabric (the white).
Ta-Da!
When you have as many blocks as you need, sew them up
Have fun!