It is really easy, you just need to know a few different stitches, be able to do a bit of maths so you can work out the number and spacing of the pleats, and fold cloth in straight lines along a thread.

It helps if you have a couple of bags of safety pins and a tape measure, a flat surface to measure on, a steam iron and ironing board. I use quilters pins and fabric marking pencils when measuring plain fabrics - and a long ruler rather than a tape measure. With a patterned fabric you can use the pattern rather than measuring.

The type of cloth used for traditional kilts seems very forgiving, you can, apparently, hand sew a kilt, wear it a while, then take it apart, iron the creases out and start again, and there is little evidence the cloth has ever been worked on. Finer cloth would have needle marks. I have made make multiple adjustments and alterations and put in tacking and basting threads to help with the folding and holding of the cloth, and as long as the threads do not get pulled awry nor any thread in the cloth is cut, all will be well.

If you use a cloth with man made fibre in it can be damaged by using the iron too hot, giving it a hard, melted edge rather than a crisp pleat, or a permanently polished look again by melting the fibres - but that is just something you learn with a bit of practice on spare bits of the cloth.