To implement a footer that sticks to the bottom of the viewport even when there is little content on the page use the l-site element (that should be a wrapper around whole contents of the page and direct child of the <body> element) with l-footer--sticky inside it.
View full screen example of the website layout with sticky footer.
To import just this sticky footer into your project, copy the snippet below and include it in your main Sass file.
// import Vanilla and include base mixins
// this only needs to happen once in a given project
@import 'vanilla-framework';
@include vf-base;
@include vf-l-site;
For more information see Customising Vanilla in your projects, which includes overrides and importing instructions.