A method includes fixing an axis between a first arm with a lengthwise slide for a first vertex pivot and a second arm comprising an angle indicia proximal a first end and also a lengthwise slide for a second vertex pivot. The axis is configured to interlock the two arms proximal respective first ends in a fixed angular relation based on the angle indicia. A first half of an elliptical arch is scribbed on an elliptical template blank via a scribbing point proximal the axis by sliding the first arm along the lengthwise slide on the first vertex pivot and sliding the second arm along the lengthwise slide on a co-vertex pivot. A second half of the elliptical arch is scribbed by sliding the first arm along the lengthwise slide on the co-vertex pivot and sliding the second arm along the lengthwise slide on the second vertex pivot.