Designing a theme at your own is not an easy task. It requires a lot of efforts for building a custom theme at your own. The person must have programming skills and control over web programming languages. Even after that, it takes a lot of time to make a theme without any errors. testing them and then finalizing it takes time. That's why a person who is in a hurry can't rely on this process. Rather he/she should buy a theme from a developer or us ea Free Theme available on the internet. In this way, the site could be launched too early as compared to building and using your own custom theme.