So IKEA in my country decided that they would sell you the BESTA storage units with MITTLED LED spotlights as a bundle, but that they are outright silly and their installers cannot install the featured lights nor give you any help with it during installation. You need to install them yourself, but once the units are mounted to the wall you cannot do this.
In order to DIY the job as they build the cabinet, I have created this jig for quickly marking the LED position in the center of each unit
To print this on most printers, use your slicer's cut feature to cut the oversized pieces and add joints accordingly, like the example given
The author marked this model as their own original creation.