Not trying to take business away from anyone, but I've made a few myself and it's not rocket science.

Now, the "belted plaid" (as they've always called it, though nowadays it's often called, somewhat incorrectly, a "drummer's plaid") which has been very popular with military and civilians over the last 200 years is another issue, being a rather complex thing to make. I've made those too.

But a "fly plaid" is simply a square of tartan fringed all round.

I rolled the fringe by

1) using a comb to pull out the cross-threads

2) seperating out the threads to appear in each bit of fringe, each "rope" one might say. I did this carefully, not by a strict count of the threads but using an artistic eye to select the right colours for each rope of fringe.

3) seperating each bit of thread into two, twisting each one direction, the putting the two together so that they self-twist into a little rope.

4) finish off each rope of fringe with a knot. (I used to have a Scottish-made plaid with no knots, and it felt like the tip of each rope was dipped in starch or glue or something to keep it from unravelling.)

Here are two plaids I made back in the 80s, a long plaid and a belted plaid