First I took the 12 inch by 12 inch piece of thin plywood I had left from a trip to Michael's.
I painted white acrylic craft paint over the surface. I painted two coats.
I then--because I'm lazy and didn't want to hook up my Silhouette (someday I'll have a desk where it is permanently set up)--handdrew a heart on paper, cut it out, and then traced it onto the wet paint. I wasn't concerned about the mess in the heart because that was getting painted.
I painted the inside of the heart with chalkboard paint and let it dry.
I covered the edges with glued red ric rac. Voila! This was fast, easy and will entertain him for hours.
Have fun writing messages, my little buddy!