silverstripe-webpack/app/templates/Includes/Content.ss

<div class="page-content">
	<h1 class="page-header">$Title</h1>

	<div class="page-content">
        $ElementalArea

        <% if $Form %>
        <div class="form-container container">
            $Form
        </div>
        <% end_if %>

        <% if $ExtraCode %>
        <div class="extra-code extra-code-page">
            $ExtraCode
        </div>
        <% end_if %>
	</div>

</div>