Trim photocopies of the triangles foundation paper pattern a scant 1/8" BEYOND. Use rotary cutting equipment or scissors.
Cut fabric rectangles slightly larger than the trimmed paper rectangles. Cut one each BACKGROUND and COLOR rectangles.
For this project, you will need 8 background and 1 each of the 8 value colors.
Layer the fabrics and foundation as shown (stacked with fabric edges aligned, paper within fabric rectangle edges):
bottom layer = color fabric FACE side up
second layer = background fabric Face down
top layer = paper rectangle, PRINT side up
Simply hold the layers together as you take the layered unit to the sewing machine, or use a couple of straight pins in the "open" areas away from the stitching/cutting lines.
Adjust machine stitching LENGTH to 8-10 stitches per inch, or about half the length of regular piecing and sewing.
Stitch EXACTLY on the dashed stitching line, moving and rotating the layered unit at the end of the shown line to begin the next line section. Also stitch on the other dashed line, pivoting to redirect and complete the second half of the line.
TRIM: use rotary equipment to precisely trim on ALL solid "trim" lines, including the diagonal lines. Find a sequence for best efficiency to do this.
PRESS: place paper side of each unit on ironing surface, open the triangles, press colored triangle away from the seam.
REMOVE PAPER: fold along the stitching, then peel away seam allowance paper at stitching perforation; remove triangle, too.
Here you see the completed unit. Triangles of seam allowances (sometimes called "tails" or "ears") will extend beyond square raw edges. Trim these away even with raw edges.
Adjust stitching length back to normal. Complete piecing of blocks, using these units in designated positions.