Gather these parts (single buttress parts shown, double buttress parts will be taller)
This step and the next will need to be done in quick succession as you'll need to be able to do it before the glue sets.
Glue the side plates into the back.
Glue the angled top into the back and sides.
Glue the front panel on
Prime with Rust-o-leum Profesional Enamel flat black and paint as normal with hobby paints.