How can one set up a Play Framework 404 (OnHandlerNotFound) page in Play 2.2?

So I've checked around and I've looked at various sources but I've failed to find a way to render a specific page when a handler isn't found.

I've gotten to this point in Global.scala:

import play.api._
import play.api.mvc._
import play.api.mvc.Results._
import scala.concurrent.Future
import views.html._

object Global extends GlobalSettings {

  override def onHandlerNotFound(request: RequestHeader) = {
    Future.successful(NotFound(
      ??
    ))
  }

}

I'm just unsure what to add at the "??" in that code to render a specific html document when a Handler isn't found. I've tried a few ways but an error always pops up.

Thanks.