So my solution started with giving my students the option to come in during their recess time to complete their art. What I discovered, however, was that in most cases I was in the middle of teaching another class when they came in or I couldn't find their artwork in the stacks of art I had to grade or it took so much time to get the supplies they needed out for the lesson that they barely had any work time (recess is 15 minutes long at our district).
After struggling with this, the solution became so obvious I couldn't believe I didn't think of it from the beginning. I set up a table in the back of the classroom. At the table I have a basket labeled Art Catch UP Basket. Students that think they are wanting to come in can place their art in the basket. BINGO! Each piece of art is labeled with name and class code. I also place the date it lands in the basket on the back (anything that is over a month old is sent back home-I figure if they haven't came in to finish by then, they probably never will). I keep my eye on the projects that land in the basket and set up the supplies that are needed to complete the lesson or leave a note where they can find the materials they need in the classroom.
Student now know where to go and find their work. This system saves time for everyone and doesn't interupt my teaching from another class. Best of all, students are completing art and turning in the masterpieces I knew they would be all along!