I think Woodsheal has brought up an excellent observation, one that I pondered a few times myself. Somehow, I can't see someone laying on the ground and pleating a length of tartan, then pleating the aprons as well before belting it on.

However, I have heard of (and tried) the method of throwing the pleated plaid over a shoulder and then adjusting it. All I can say is that to make it work takes a lot of effort and perhaps those of old had practiced it enough to make it work. I have laid it on the floor of a British military wedge tent, and on the dew-wet grass, but after seeing the bogs of the highlands, I can't see as how they would have done the same. But then again, if they took it off to use as a blanket while sleeping, gathering it up in some rough pleats to put back on before wearing is perhaps reasonable.

I've also thought that perhaps the artists of the time have used some artistic licence in trying to show a what was considered a "primitive" garment. It doesn't take too much effort to visualize a length of cloth just gathered up and belted on when you see these paintings. Also, after they've been worn for several hours, especially if any physical effort has been involved, the plaid does begin to look a bit disheveled.

A good discussion and I'm enjoying the reasoned comments being offered.