From what I can see, you are just laying the tartan cloth on top of the denim, making the denim kilt with the tartan sewn into the pleats. This is a great idea, especially since the denim is obviously a heavier fabric than the tartan!

When I made mine, I had to sew together the strips of cotton and wool, because I couldn't have the wool touching my skin any more than absolutely necessary (itchy, itchy, itchy!). As it is, the wool still makes some contact, so I have to wear substantial stockings to be comfortable. Next time, I'm stealing your idea-I'll make a cotton kilt with the tartan wool sewn into the hidden pleats.

Thank you!

Be well,