Look, ma, no screws!
This is a remix of https://www.thingiverse.com/thing:2761965 to avoid having to use screws, but instead uses two simple clips that go in the v-groove profile (insert, then turn 90º to attach) to which the main part clips on.
STRUCTURAL PART! Don't be cheap on the infill, 40% or better, please
CC License - Attribution - Non-Commercial - Share Alike: Non Commercial means you can´t charge for the files, but you may charge a reasonable fee if you print this thing for someone else.