Install NANO server from USB Key
Possibility to install nano server like a Datacenter or standard server on a physical server
-Mr Happy- commented
Deploy Nano Server gui now allows this quite easily.
Sean Kearney commented
You can use the DeployImage module for PowerShell which was designed to create Bootable USB media with Nano Server on it. It's in development and accessible from the www.powershellgallery.com / Directly from PowerShell 5 (Install-Module DeployImage) or from Github on https://github.com/energizedtech/Deployimage
Tim Cerling commented
Installing Nanoserver from USB is possible today. Because preparing Nanoserver for installation differs from preparing Datacenter or Standard for installation, the procedure is a little different, but it is possible. First you need to create a USB with a WinPE image that has enabled PowerShell. Then you add the Nanoserver wim. Here is a blog link that is part of a series on a module that was created to make this easier. It is the last in the series, but it has links to all previous posts to cover everything needed. If you don't like using the blogger's module, his process can be readily adapted to using the Nanoserver Quickstart method shown in TechNet. FWIW, I gave it a try and was successful in deploying Nano from a WinPE boot.