The Buttercream WordPress Theme by Caroline Moore is wonderful, but I needed a Left Sidebar to display the list of categories, as you can see on this website. So I built up a child theme which displays a left sidebar while browsing the homepage.
You can download it here to get the basic idea behind it in order to build your own child theme, or you can just use it directly. If you need more information on how to add a sidebar, I strongly recommend you to check this post from the Buttercream support forum. And if you’re very new to WordPress and wonder how to install a theme from a ZIP archive, you better check this page.
Hope this helps!