Thereafter, I marked the grooves for the block magnets
on both boards.
With a router, I milled the 1,5 cm deep and 1,2 cm wide gaps into the wooden boards.
Then I was able to carefully line up and embed the block magnets before I secured the magnets with wooden picks, chipped wood, and PVAC glue.
I glued the two wooden boards and pressed them together with screw clamps so they would stay in place.
After the glue dried, I sanded the sides of the wooden block down with a sander.
To eliminate rough spots from sanding and end up with a smooth surface, I worked on all sides (except the bottom) with medium (100) and then fine (200) sandpaper.