Why the hell do you immediately think of slavery? You don't force people to do anything. If you need work done, you pay people to do it. Obviously.
And since workers have a guaranteed income to fall back upon, employers have no choice but to pay a fair wage. That's the entire point.
Seriously, if you want to understand UBI, there are whole studies available online for your reading pleasure. There are dozens of books on the subject. Your question isn't mysterious or insurmountable, but worse, it's not even insightful. It reveals that you've never given it the slightest consideration or study. Do some work. You were down voted because you're so wildly off-base as to not even be wrong.
Since you brought it up though, what do you think our current society intends to do with us besides slavery and genocide? And how do you propose to stop it?