Sidebars appear to the right or left of the content when they fit, or collapse into a content header or footer on narrow screens.
Sidebars can be implemented as a region in the page template, configured in the block layout.
Sidebars could also be implemented in a layout or another component.
A convention that could be used is using the left sidebar for global blocks, and the right sidebar for content specific blocks.
Here is the reddit layout, with a fixed width sidebar that can be collapsed to the side at full width, and completely hidden and toggled with a header button on mobile.
Will a left hand nav conflict with Drupal's admin toolbar/navigation?
Current display:
How should the sidebar width be set?
Tab order
Consider the tabbing order and skip links.
If the drawer is additional navigation, it can come before the main content in the html. Use a skip link to avoid irritation.