Skadis shelf, clutch 90 degrees

A shelf with a 10% infill normal size and small 15% infill cross hatch, also serving as a connector for two board at a 90-degree angle.

No upper and bottom layer.
You can also try another option infill (objects shelf) viz. foto.

used with  https://www.ikea.com/cz/en/p/skadis-connector-white-10320789/

Other things from the Skadis series:

https://makerworld.com/en/collections/1848383