How to build and deploy an Ionic App for Browser.
This will work for Ionic 2.x and Ionic 3.x and will make a folder structure ready for deploy.
You need to run (depending on your Ionic Cli version)
ionic cordova build browser --prod
ionic build browser --prod
Then you need to use what is inside
Be aware that depending of what your App does, you could need to use a HTTP server to be able to see it locally.
There is also a direct way using npm
npm run ionic:build --prod