C&J handgrade, like other Northampton makers, cuts a horizontal flap, makes a channel, sew outsole, then glued back.
See: John Lobb
Vass, cuts vertically into the sole, making a channel without removing leather with tool, sew outsole, then press down. Similar method is used for SC.
See Saint Crispins.
West End bespoke makers slice sole open from the edge, spread open a flap, make a...