You can get the latest version of the Mojave installer from the Mac App store. The procedure has changed slightly this year due to a change in Apple’s createinstallmedia tool. Here’s this year’s version of my annual how-to guide.
It’s great for installing the OS on multiple Macs, because you don’t have to download the ~6GB installer onto each computer, and it serves as a handy emergency disk if your Mac is experiencing problems. I’ve long recommended creating a bootable installer drive-on an external hard drive, thumb drive, or USB stick-for the version of macOS you’re running on your Mac.
