We've recently noticed that the latest Big K disposable BBQ's don't have air holes around the sides anymore and the food doesn't cook so well. We contacted the company to ask why and they replied that they don't put holes in any more because embers can fall through, creating a Health & Safety issue.
We have since tried several different ones from various sources and some have holes and some not. We make holes in the side if we use one that doesn't have them.
Thanks for all the ideas about stands. On CL farm sites you can usually find a slab of concrete or bricks to use, but it's not so easy elsewhere, unless there's a dedicated BBQ area.