Take your finger and starting at your collarbone, trace the line followed by a button band that goes down the front of a cardigan. Once you get to the bottom, trace your finger across the bottom edge of your imaginary cardigan. Go completely around your body. If you are a contortionist, you can follow around until you reach the center back, then trace an imaginary line up your spine to the base of your collar. The Taco is cast on in a long strip that follows this line.
Corners formed by double decrease miters define the bottom center corner at both front and back.
The two halves, left and right are knit one at a time. They progress from this defined outer edge to armscye, and march from there out to the sleeve's cuff. The mitered corner decreases form the garment's basic shape. I chose to knit mine with no seams whatsoever. After the initial collar shaping, I joined my rounds and knit circular fashion.