Hi jonc1
In case that you want to have off-canvas like that, you can consider to us JA Page Builder with a Joomla template which supports off-canvas like T3 / T4 based templates.
With this way, you can create pages via JA Page Builder and in the menu item settings of this page builder, you can assign that menu to T3/T4 template style so that the header + footer sections will be from templates, the main content will be the content you added from JA Page Builder.
Regards