boxes/_layouts/default.html

{% include header.html %}
<div class="container container-left">
    <div class="row">
        <div class="col-md-3 hidden-xs">
            {% include sidebar.html %}
        </div>
        <div class="col-md-9">
            {{ content }}
        </div>
    </div>
</div>

{% include footer.html %}