In the perfect world a coil would be perfectly layer wound. Some attempt it, it takes a long time and extreme patience. Others just random wind the things in a few seconds.
The end result often is that the perfect coils are so neat that the thing can be assembled with a smaller air gap and quite often the thing runs stalled and the output is disappointing.
Most machine winding, especially in machines with slots can't be perfectly wound. The wire is tolerant and often the stacking factor is not much different unless you make a real mess of it.
Just do the best you can and try not to let turns slip down several layers, you will most likely not be able to layer wind it beyond 2 layers without spending many hours on each coil ( never justified). With low voltage the wire can stand the voltage stress of turns separated by at most a few volts. Nobody seems worried about the worst case and I haven't seen anyone take any precautions with bringing out the inside connection over the end of the coil ( dreadful practice but universally done).
It is difficult for people not familiar with the electrical machine industry to have a feel for what is normal. I see extremes here where some take great care to aim for perfection and others do things that the older wire coverings that I was brought up with just wouldn't tolerate.
Flux
