Cutting & Sewing directions:

For #3 triangle, cut 1 square of dark, 6 7/8". Divide diagonally to make 2 triangles.

To make half square triangle units:

Cut 2 squares dark, 1 square light and 3 squares medium, each 3 7/8". Pair them up, right sides together as 1 M/L and 2 M/D. On the back of the lighter square of the pair, draw a line diagonally from corner to corner. 1/4" on each side of that line, draw 2 more lines. With 2 squares right side together, sew on the two outside lines and cut apart on the center line. Set 2 of the D/M units aside while you make the 4 patch corner units.

Cut 4 light squares, 3 1/2". (#2)

 Four Patch Corner Units: Sew a #2 light square to the side of each of 2 M/L and 2 M/D half square triangle units. Refer to Dark/Light diagram for correct placement. Then sew a D/L to a L/M unit together to make a 4 patch unit. Repeat with other 2 D/L & L/M unit. Set aside and made the Triangle corner units.

Sew a light triangle to the side of on of the D/M units you set aside earlier, matching short side of the light triangle to the short side of the Medium triangle. Repeat on the other side with another light triangle. Do the same thing with the other D/M unit. Sew the resulting triangles to the large dark triangles, matching long sides. Sew carefully because you have some bias edges here.

To finish assembly, sew a 4-patch unit to each triangle unit (check placement by the Dark/Light diagram) and then sew those two units together.