Start by picking a project that has a section you’d want to feature kid art. I recommend starting small like the neck ruffle, a pocket, or border hem.
Cut the pieces out and then tape the piece you want them to decorate right side up to a table. This will stabilize the fabric making it easier to draw on. I also recommend taping over any space that you need for seam allowances (you don’t want to cut off their masterpiece). I did not do this but both girls made designs that had a center so I wish that I wish that I would have marked the center on their fabric. T’s was a bit off so I just hacked off some of one of the ends of the ruffle so it would fall more center.
Then let them go at it!
After that all you have to do is assemble your project like normal.