How to block off access to under beds?

I would like to prevent Cindy from hiding under beds.  She does have plenty of other hidey holes to disappear into, I just really don't want her under the beds for a variety of reasons, the main one being that when she gets under a bed she stays there and broods and gets even more nervous. If she's out with us, or at least in a reasonably accessible hidey hole, she recovers from her anxiety much faster.  Any suggestions?  Everything we've tried leaves enough of an opening that she can squeeze into.

The only way that I've ever been successful at this was when I removed the bed frame and put the mattresses directly on the floor. Either that or close the door to the room with a bed and don't allow her in there.

I have plastic storage containers under my bed. I store out of season clothes under there and it keeps the cats out too.