Dia Dhuit, Arlen!

Fly Plaids typically come in two different sizes: 39" (99 cm) square or 54" (137 cm) square.

They are fringed on all four sides in one of two ways:

Standard fringe: involves pulling out threads to achieve the desired length of fringe (not too long, else it will get ratty quickly).

Purled fringe: This requires much more effort, as you must pull out more threads than the standard method. Then, you must twist the threads together and tie them in an overhand knot at the end. Much like the finished end of some blankets.

As for sewing, it's really your choice. Some kilt makers sew one corner into folds/pleats. This is the corner which passes under your epaulette. Other kilt makers, like myself, don't bother. By leaving it square it can be ironed in the future and it can still be used as a shawl or wrap if need be.

Uh . . . I just re-read you post and realised you had dismantled a kilt for the material. Unless it was made for an extremely tall person (8' + tall ) it won't yield a sufficiently wide enough piece for a fly plaid. However, you could probably make some sort of day plaid out of it.

Hope this helps!