Although I was not too successful with the original design I made this holder which I found more convenient.
Works with 5mm x 5mm x 5mm cubic magnets like these: Example
No Glue was required for me.
Tips for assembling:
Use a flat object like a ruler to firmly press the magnets inside.
The author remixed this model.
Replaces the Base_KnifeBlock.stl of the original design