How clean is "clean"? Little to no visible wires? Or just neat and orderly? Mounting the fuse panel like Achipmunk says is the best place to start for either one.

You can hide a good amount of the wiring in the frame rails with wire loom and clamps to keep it up in tight and out of sight, and the engine wiring can be run along the back side of the engine.

To just make it look neat you simply start at the fuse panel and run one wire at a time so that you can tie them in a neat bundle and then cover them with a wire loom and secure it with zip ties.
Either method just takes some time, you may have to mess with it a couple times to get it just right, but either way isn't terribly difficult.

1956 GMC 370 dump " 'Tater "
1970 VW Volksrod "the Black Bomber"
2007 Chevy Avalanche
2020 Jeep Cherokee Trailhawk,
2005 Harley Davidson FLHTCUI

I dig all cars, old and new, whether they were hammered out of American iron, German steel, or Japanese tin cans. Being unable to appreciate them all is missing out on a world of great things.
But thats just MY opinion! :P