#темплейт
{% extends "layout.html" %}
{% block body %}
<form action="/delete" method=post>
        <input type="submit" name="submit" value="Удалить выбранные">
        <ul class=entries id="documents_list">
        {% for doc in list_docs %}
                <li><input type="checkbox" name="do_check" value="{{doc}}">{{doc}}</li>
        {% endfor %}
        </ul>
</form>
{% endblock %}

#приложение
  ..
  return render_template('vk_doc.html', list_docs=list_doc)
@application.route("/delete", methods=['POST'])
def check_pages():
        page_ids = request.form.getlist("do_check")
        list_doc=[page_ids]
        return render_template('vk_doc.html',list_docs=list_doc)