The heat vents should be as close as possible to the heat source under the heating element. If you will place the pad, you should also place the heat vents at the periphery of the component.
Small-diameter through holes with a diameter of about 0.3mm is suitable and can be filled by electroplating. And the spacing of the heat dissipation holes is about 1.2mm, arranged directly under the heat sink on the back of the package.
Más lectura: Tecnología de PCB aplicada al ensamblaje de PCB LED