In the below video tutorial, I will show you how to create a bootable USB flash drive, that you can use to install macOS Sierra on an external hard drive, another USB flash drive or inside a virtual environment.
You will need :
1. USB flash drive (16GB recommended)
2. macOS Sierra app
Copy and paste this code in Terminal and make sure your USB drive is named SierraInstaller :
sudo /Applications/Install 10.12 Developer Preview.app/Contents/Resources/createinstallmedia –volume /Volumes/SierraInstaller –applicationpath /Applications/Install 10.12 Developer Preview.app –nointeraction &&say Done
Remember : DO NOT install the developer preview on your main computer! It is not stable yet.