Creating a Blazor Layout

Any content you intend to act as a layout template for pages must descend from the LayoutComponentBaseclass. To indicate where you want the content of your page to appear you simply output the contents of the Body property.

@inherits LayoutComponentBase
<div class="main">
  <header>
    <h1>This is the header</h1>
  </header>
  <div class="content">
    @Body
  </div>
  <footer>
    This is the footer
  </footer>
</div>

References
https://blazor-university.com/layouts/creating-a-blazor-layout/
https://blazor-university.com/layouts/using-layouts/