Bootcamp windows 10 without a USB

Hello, I've got a early 2015 macbook air running os x mojave. Based on this I should be able to run bootcamp without the need of a usb since they added the new feature and I seem to pass all the requirements(Install Windows on your Mac with Boot Camp - Apple Support). When I open the Bootcamp Assistant it seems to be telling me otherwise sadly I only have a 4 gig usb(requires 16gigs). I was wondering if I had to do something to be able to get the menu that would let me bootcamp windows 10 without a usb key. I've already downloaded the iso file from microsoft website and tried running a virtual box but even after tweaking the settings it was still too sluggish for my taste.

I've found this older thread where Loner T was helping a guy in the first page of the thread. How to use bootcamp without a usb)

Anyhow, he eventually gave the rude guy(haha) a way to do it with a 1-2gig usb by burning the iso into a partition(which is often seen on cheap windows pc bought at bestbuy that come with the iso burned into a small partition to make it easier to reformat, etc). Anyhow, after trying to even start following the instructions, i've noticed that the first file that I need to copy on the smaller usb wasn't where it was mentionned which is probably because the post is from 3 years ago and they've changed how mac os works or where the file is located. It would probably be much easier if you could help me Loner T since I see you still answer questions even to this day since you wrote the solution in that thread above. Or you seemed very knowledgeable so maybe there is a way to install windows 10 via bootcamp on my version of macbook without having to burn the iso in a small partition.