That's the key. It's not so much the bolt holding fixture as it is being able to index it with some level of precision.
There are cheap x-y tables available, but the problem is they are usually sloppy with a lot of backlash, and the travel is not precise. You often have to get a dial indicator in order to use them. And you can't back up during an operation because the backlash throws everything off. Travel in one direction only when doing work.