I combined a few model's geometry to make a 5 part assembly into a single part.

https://thangs.com/designer/notsam/3d-model/2x7%20WallControl%20to%201x4%20Gridfinity%20Adapter-63060

https://github.com/aderusha/DDD-Printable-Wall-Control-System

I like the Gridfinity system a lot, but I was frustrated with the end quality of using the DDD wall control brackets along with this adapter, so I made them into a single part. My version also prints with no supports or assembly required.

Print with the "Top" side down and use an arachne based perimeter generator because there's some thin walls on the first layer. I would also recommend printing the first layer slowly (10mm/s) to ensure bed adhesion, as there isn't much surface area.