Take a look at this exhibit in our museum, of an outfit dating to pre-1854.
http://www.scottishtartans.org/muirhead.htm

Those orange things in the lower left of the picture are garter flashes. Not quite like the modern elastic ones, but they are not self-tie, either.

They are made from woven ribbon, with the decorative "flash" sewn onto a garter band, made from the same woven ribbon as the flash (not elastic). I don't recall now just how the garter fastened (or if the fastening mechanism has even survived with it) but I can check when I am in the museum on Monday morning if I can remember to.