Building a WordPress website can take anywhere from a few hours to a few days depending on the complexity of the site. The majority of the work, however, is typically spent on the front-end of the site.
This includes designing the layout, creating the content, and setting up the blog or other pages.
Due to the open-source nature of WordPress, there are many community-contributed plugins that can make the building process easier. In most cases, however, it is still possible to build a website from scratch if you are motivated and have the necessary skills.