I only know of two ways to make that rectangular unit - possible three:
Sew strips together and then cut out the unit.
Sew two triangles together. Be sure to mark the end points of the seams - match them up before sewing -you will have tails sticking out when the triangles are correctly lined up.
Paper piece.
The way you want to do it - you get the kite piece as sewwhat85 just said.
Last edited by bearisgray; 07-12-2014 at 10:38 AM.