At the bottom left of this image, you can see where this string-pieced quilt block was started. The striped fabric and green fabric were placed, face-to-face, diagonally along the lower corner of the foundation block, then both were stitched along their inner edge to the foundation. Next, the green fabric was folded over, pressed, and the yellow fabric was placed on top of it face-to-face. They were stitched down to the foundation fabric as before, and the process continued all the way across the block. A line of stitching around the perimeter of the block, part of which can be seen at the lower left, held all the edges down neatly.

Pattern: 
String Squares, detail
IQM, 2003.003.0001