admin_templates_controller.rb

class AdminTemplatesController < ApplicationController
  def new
    @admin_template = AdminTemplate.new
    render 'admin/templates/form', layout: (not request.xhr?)
  end
end

show.html.haml

= @product.name

= link_to 'Add Template', new_admin_template_path, data: { toggle: 'modal', target: '#modal-window' }