How do I make a new account on clash Royale?

If you are using an Android device, you need to go to the Settings -> Accounts -> Add Accounts and sign in with Google.
After that, you need to load the game and head over to the game settings. Tap on the Green button twice and it will load all the Google accounts added to your device. Choose the one you want.

Head over to the Settings and Tap on the “Connected” button twice. Add your new Google Account.

Open Game center on your iOS device. Login with your new Apple ID, once you are logged in you will be asked to make a new account on clash Royale.

Open your Google Account page. Head over to the Apps and Games. Look for Clash Royale and remove it from your current account.
Log-in with your new Google Account and head over to Google Play. Open Clash Royale and try connecting it with your new account.

Yes, you can. Delete or Un-install Clash Royale from your iOS or Android device.
After that head over to the Clash Royale official website.
Log in with your account then click on “My Accounts” -> “Delete account”.

Launch Clash Royale, Settings, Accounts, Email, ( Add your new address ) Save.

You can always download Clash of Clans on a new device and make a new account.
But if you want to make a new account on the same device.
Then you have to delete the Clash of Clans and re-install it.