Here is the right & left sides of the radiator cover - Pocket holes, mitered corners, wood glue (using the handy dandy tape trick) ...

Handy Dandy Tape Trick: After cutting your 45 degree miters you line up your corner nice and tight, tape it, and lay it out flat using the tape you can put on the glue and get the corner back into place easily.This trick is real nice for boxes as you can just roll it up and the tape acts as a clamp