Lots of cable tidies already exist and a lot smarter looking and convenient than an ugly plastic box full of holes.
Doubtful you could give those away .
OK so no one else has asked, why the hell are you using that type of plastic box for electrical connections?
They have an absolutly zero fire rating, proper boxes have self extinguishing additives to ensure the box does not set on fire.
I hope to god that your not charging anyone for this lash up, the insurance company will have a hissy fit at the use of unsuitable equipment.
If you really have to be a cheapskate, then I'd go for the stepped drill option myself, and use nylon glands rather than leave gaping holes for little creatures to crawl into (and cause a fire when they make a nest).
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local