Another old skill, a good one: cable lacing. Before there were Velcro strips, before there was split-loom tubing or even zip-ties, 'way, 'way back -- and on fiber-optic bundles, even now -- there was cable lacing, the art of turning a jumble of wire into a neat bundle* using flat, waxed string or similar, in the proper knots.
There's an art to it and a learning curve; you can still learn it, thanks to a tip from a clever lurker, who pointed out Make: Lost Knowledge: Cable Lacing! And now I've linked it for you. Enjoy!
Older ARRL Handbooks also cover this skill.
If you can't find lacing twine, look for waxed saddler's (or leatherworking) thread, a heavy thread (almost string) which will work as well. Might as well pick up a cake of beeswax at the same time, it's handy stuff.
* It kinda has to be neat to start with. This holds true for any other cable-bundling method, too. If you start with a rat's nest and mash it together with whatever, it'll just be a worse mess. Neatness counts when you're trying to figure it out later!