Blue and yellow binding strips form a lattice. Yellow binding holds it all together along the outside edges where it's sewn to the apron body.
I can't quite figure out how this was sewn since the stitching runs over areas that are open underneath. Any thoughts, dear readers? Would it help to see the back side of it? No matter how it was sewn, it's really pretty and unusual.
You could use the same basic idea to sew the strips onto a background fabric—creating a three-dimensional lattice. And then add appliqued or fabric flowers on top. I'm envisioning a pillow here if you couldn't tell :)
Updated to add a link to a photo of the back side.