Can I duplicate the fixed sidebar without plugin?

Hey,

The provided site isnt mine. I like the sidebar with the name "best vpn deals". What is the best solution to immitate that. Design wise + that it is on every page?

Edit: My little solution so far is to add this to additional CSS:

@media (min-width: 769px) {
.site-content {
  display: flex;
	}
	
.inside-right-sidebar {
  height: 100%;
	}
	
.inside-right-sidebar aside:last-child {
	position: -webkit-sticky;
	position: sticky;
	top: 70px; /*Adjust position */
  }
}