Cut:

Purple:
2--3 1/2" x 3 1/2" squares
2--1 3/4" x 1 3/4" squares

Yellow:
2--3 1/2" x 3 1/2" squares

Draw a line corner to corner on both of the 1 3/4" purple squares. Place on yellow square and sew on line, as shown in the second picture.

Fflip over and press.