where were you taught this? to remove the heat you want to suck it out of there, not keep it in; and you want to draw in cool air at the same time, so you get a circular flow of cool in from the bottom, and warm out at the top, also heat rises so it's a natural flow assisted by the exhaust fans; dust will be blown in by the fans in your scheme, much more than any drawn in 'at the seams', which won't happen since air will be drawn in the holes drilled at the bottom.

if dust is a concern put some thin cloth over the intake holes and remember to vacuum them occasionally