I wanted to offer you a nice rubric, originally created for second grade but customizable to other grades with the empty template. This is a concept used by many others. I wanted to create an easy to use rubric for the students and me. Enjoy conferencing with your students! As part of teaching the writing process, it is important to teach ownership of the writing process. By asking students to reflect on their own writing you can instill that sense of responsibility and pride in them.
A suggestion when doing this is to allow for time toward the finish of the writing project, perhaps when students complete their pictures, to conference with each individual student after they complete their version of the rubric. They may need to do it as you speak with them. Summative or Formative, this is an effective tool for student improvement and joy of writing.