The design features a knitted cover, created on a machine for making clothing and washed at a high temperature to shrink the wool.
Buttons hold the resulting cover around the bent steel and wood frame.
Here's a little text from Established & Sons:
Jumper consists of one continuous oversized woolen knitted cover, with qualities very much like that of a jumper, including buttons that fix the cover together on the underside of the chair, once the knitted cover is wrapped over the solid wooden structure and bent steel legs.
The cover is knitted on a ‘Knit and Wear’ machine that is skilled for clothing garments, but this is where the fashion and design production processes divide.
Once the garment is completed it is then run through a high degree wash to attain a seamless and upholstered effect eradicating most of the stretch from the wool but presenting a high quality fabric that layers the structure with precision and rigor.