I followed the old Eagle/Oshpark directions. It's a long pad (hole in center), drill adjusted to what I wanted, and milled to the length I wanted at same width as diameter of the hole. Of course, the pad was named "GND" so it would be included in the pour.
That design is in the library file (package), so I didn't need to go through those machinations on the board. I have other plated slots for attachment clips and passages done the same way, i.e., as devices, or they can be drawn on the board.