Set it on a table in open air
If you want a really cheap case that is big enough to house a card like that, this one will probably work.
It is made out of thin metal so it can be flexed a little, but if you put a fan into the front it could get the job done at least.
Like Blacklash said though, you don't want to put the most expensive graphics card there is into a cheap case where there is no fans causing it to overheat. The PSU is also going to be a very important decision if you want a card like that.