If you haven't done it yet, first go to The Zephyr getting started guide and install all dependencies (I'd recommend following the path with the virtual python environment).
This repo contains a stand alone Zephyr application that can be fetched and initialized like this:
west init -m git@github.com:larsgk/simple-web-zephyr.git --mr main my-workspace
Then use west to fetch dependencies:
cd my-workspace
west update
Go to the app folder:
cd simple-web-zephyr
There are a few scripts for building and flashing the nRF52840 Dongle - run them in this order:
compile_app.sh
create_flash_package.sh
flash_dongle.sh
Note: You'll need to get the dongle in DFU mode by pressing the small side buttton with a nail. The dongle should then start fading a red light in and out.