There might be times when you need full flexibility like a blank canvas on some pages / posts and do not want header / footer to appear. Astra allows you to disable these through the Meta box settings of the specific page or post.
As you can see in the screenshot, you will find a meta box named Astra settings in your backend. You can disable the title, header or footer from here.
Note: If you are not able to see Astra Settings as shown above, you will need to enable this through screen options. Please refer this screenshot.