I'm currently working on a tweed kilt, and thought I would share my construction technique for the strap hole.
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You will see that I have laminated a triangle piece of leather stitched it and punched a hole to facilitate the under apron leather strap to come through.
To the left of the hole you will see another triangle of leather. This is sewn to the underside of the covering pleat of the strap hole. When the strap comes through the opening it will rub against the leather instead of the wool and transferring the wear to the leather instead of the wool when the strap is pulled tight to the buckle.
The seam you see in between the two leather pieces is where I had to join the fabric, it will be buried in the pleat.
Cheers