npm run electron-dev - This will start the electron react-app
npm run electron-pack - This will package and build a ready for distribution Electron app. The -l command builds for linux. Can be changed for other builds such as mac -m or windows -w.
To be able to run a local json-server I had to save the server.js and db.json in the public folder for it to function in the build. In development you can install the json-server as a DevDependency and have the server.js and db.json in the root of the workspace as usual. However for this project I wanted to have the build function properly with a local server running.
I will have to look into better ways of integrating a server.js into an electron-react app, especially if I wish to test API calls with json-server. It would be best to keep json-server as a DevDependency.