These cross over baskets are super easy to assemble.  They are approximately 2-3/4" x 2-1/2" (5" with handle) x 2-3/4" and are compatible with both 8x12 and 12x12 mats.  The file comes with the box base, box handle, coordinating mats, and the decorative paper elements shown.  The basket and decorative pieces can be used on their own or together as displayed in the photos.  

https://jamielanedesigns.blogspot.com/2019/03/cross-over-baskets.html