This is a remix from https://www.thingiverse.com/thing:3023240 to fit the Ender 3 Pro/Meanwell power supply which has only one screw at the back. It uses the original screw (if you want to).
No supports needed (if printed with 0.2 layer height or less); the hole has a 0.2 mm thick bridge over the countersink that is removed after printing instead.
You can actually feel the added rigidity in the frame after mounting.
Remove the layer of printed material over the screw hole, using e.g. knife, scissors or screwdriver.