For those who haven't watched, this show seems to be a continuation of a series on making your own "dulcimer" sandwiched in between a few songs by the second incarnation (1970) of Steeleye Span just before release of their second album Please To See The King.
The hosts idea of a dulcimer was to make a fretboard stick that would use a table top for resonance. I seem to recall this being reported as being done in Appalachia with standard dulcimers on occasion.