The best way to cut the sheathing is with a hot soldering iron. this fuses the loose ends together as it severs the sheathing to length.
The fusing aspect is both good and bad. Good in that it makes a clean cut and prevents fraying. Bad in that it no longer allows for full expansion of the sleeve, which I why I do the tuck, especially for snakes I know I will be reconfiguring later.
If you quickly insert a tapered round object into the hot knife cut ends, you can make sure the fused ends can still be expanded. You have to do this before the cuts cool. I’ve used the tips of needle nose pliers or the point of a 3.5mm plug as the flaring tool with success. DO NOT breath in the hot knife fumes!!!