Here Are some step Follow It.
1. Create a New Facebook Profile
2. Active your email address and verify your mobile number to set a username.
3. Open Facebook Via “https://mbasic.facebook.com/username/”
4. Enter spaces at the beginning of the username field.
4. Click check availability.
5. Click on set username, mostly the page will stay blank . but the trick works and we are done .
Demo account : https://www.facebook.com/%20ethical.hacker.khalil