_block_layout.html.erb

<li class="result-block <%= result[:type] %>">
  <div class="subject">
      <%=  yield :subject %>
  </div>
  
  <div class="snippet">
      <%=  yield :snippet %>
  </div>
</li>

_custom_block.html.erb

<% content_for :subject do %>
  <strong>Hello World</strong>
<% end %>

<% content_for :snippet do %>
  <em>Testing partials</em>
<% end %>

main.html.erb

 <%= render :partial => "custom_block", :layout => "block_layout" %>