[How-To] Make a double D slot?

[talvare]

Several years ago I made the components in the attached photo, and if I remember correctly (which is questionable), I made all of the D shaped cuts using end mills. I think I machined the bulk of the material using a 1/2" mill, then switched to a 1/8" mill to get into the "corners" as far as possible and then just hand filed the finished "corners".

Ted