Once you have plaited the centre whiri, then turn the end of the plait to the left (mid photo below) and weave on a taki tahi way all the way to a triangle, whenu with under side up. First whenu to the right, 2nd whenu to the left but under the first one.
Turn around and do the other side also with the end of the plait facing left (see left photo below).
Fold in a half when done and start weaving the sides in a taki tahi way. (One over and one under).
Once woven to the correct height, make then do a one up, one down and decide how you will finish the top.
An example on the left.
I am an artist and live on the Kapiti Coast. Presently I am completing a Bachelor of Maori Visual Art (Raranga). I work mainly with textiles (includes Raranga which is weaving with flax), clay and paint in pastels and weatercolours.