I am using a screened bottom board with a hive stand. On the back of the hive stand I cut the board in half so I could slide a tray inside the hive stand and below the screen board. Then I went to Dollartree and bought a cooking pan/tray for 50 cents (2/$1.00 package) and used them with regular vegetable oil. So far it works fine. The trays are not EXACTLY the size of the screen board, but they are close enough. These are the aluminum type of trays that are kind of flimsy, but my hives sit on a solid table. I imagine you could put plywood on the bottom of the hive stand to have something to put the tray on. At least, that is what we are doing to my cousin's hives to get some trays under his. He has them on two boards -front and back - with an open bottom like most people do.
If the bees knock the beetle off and it misses the pan, they get another shot at it. Must be working because I only saw one beetle in two hives on Saturday. The rest are in the oil pan.
I am just starting out as a beekeeper, so if any of the more knowledgeable guys here care to comment that would be fine. I have not seen any downsides to doing it this way - so far. I don't like to spend money if I can do something comparable cheaper. This seems like a good alternative to buying a tray for $15.00 each. I probably should use a different kind of oil, maybe?