Steps to dualboot Windows on the same drive as macOS

This is mostly for myself, it took a lot of trying to get it right. Hopefully it helps someone else, too.

This is for installing Windows on a drive that already has macOS installed (High Sierra in my case).

1. Clone and your macOS drive with Carbon Copy Cloner to a different drive.
2. Erase the whole drive with Disk Utility and set it as GPT
   
3. Create a partition for macOS as APFS and one for Windows as MS-DOS
4. Disconnect all other drives from the computer
5. Create a Windows installer USB with Rufus from a Windows machine and use the default settings
6. Boot into the USB and at the screen to select the drive, Erase the MS-DOS partition, and then click on New.