app/views/content/form/contributors/_add.html.erb
<div class="nested-fields">
<%= f.fields_for :contributors do |ff| %>
<div class="row">
<div class="col s11">
<div class="input-field">
<%= ff.label 'Contributor email address' %><br />
<%= ff.text_field :email, name: 'contributors[email][]' %>
</div>
</div>
<div class="col s1">
<br />
<br />
<%= link_to_remove_association f do %>
<i class="material-icons red-text" style="position: relative; top: 10px; left: -15px;">close</i>
<% end %>
</div>
</div>
<% end %>
</div>