The boots now have the completed outsoles in place:
Outsoles are cut from a sheet of felt (not quite as hard as the boots themselves, but definitely felted to a tougher consistency than the insoles), and have a thin layer of silicone spread over the bottoms for traction.
Attaching them to the boots was fairly easy - starting on one centre side, they were stitched down with blanket stitch, then folded across the sole and measured (and trimmed as need be) then attached to the other side. I gradually worked forward and back to the toes and heels, and stitched those last, easing in the fullness and stitching well.
With about a centimetre of wool between my feet and the floor, they feel fabulous.