You need to sew the green triangle to the cream triangle and then sew the rose triangle to the other side of the green triangle. This will make a flying geese unit that is a rectangle.
The next step would be to sew the rose square to the cream square to make another rectangle. Sew those 2 rectangles together to form a square which will be 1/4 of the block. Sew the other 3 1/4 in the same manner. Assemble the block by sewing the 4 quarters together. That is the way I would do it but others might have a different idea.