Landing Page Template
Users have the option to use the Landing Page Template, which does not have the option to add a sidebar. This is a blank slate for a page and all blocks will render correctly on a landing page.
Think of the landing page as more of a container that houses blocks. It does not have the option for a page header. It is best to set your page template first, before entering content. If you add content and then change the page template, you may experience some rendering issues.
Here is a video walkthrough of how to use a landing page and the differences between the landing page template and the interior page template.