All my bottom boards are cut out like this, but I permanently fix a piece of #8 hardware cloth as a screen. Any shallow tray can be slipped in the slot underneath the screen to trap the beetles. It has been my experience that they go through the hardware cloth just as easily as the slots, so it removes the step of slotting the piece of aluminum. I also use Safer brand DE (diatomaceous earth) in the tray instead of oil, its a lot easier to handle and seems to be just as lethal to the beetles.
"The UNKNOWN, huh? That would be SNORBERT ZANGOX over in Waycross."