You need six measurements in order to make the bliaut. They are:
This layout works in ~15" units, although the units can be widened or narrowed to suit the wearer and the fabric. For fabrics that are significantly narrower than 60", other layouts may be more appropriate. For instance, for a bliaut I recently made of 45" wide fabric, I cut the skirt pieces as shown here, but spread the maunches apart to the edges of the fabric and cut as much of the cors as possible from the fabric left in between the two maunches.
The bliaut should be comfortably snug in the torso and sleeves, full and flowing everywhere else. The abdominal part of the cors should be approximately twice the length of the wearer's abdomen in order to ruck in a period-looking manner.
The bit on trimming the skirt front will be added sometime this week, barring the unexpected.