I'd say there is no difference in setting up an unfretetd bass from a fretted.
Relief, string height, intonation, it's all the same routine, and there are not two basses in this world that would have exactly the same setup, to have a nice feel and tone.
BUT:
You need to cut down the string slots in the nut. The strings should be approx as far from the fingerboard, at the first fret line, as it used to be from the fret. You'll probably have to cut it a few millimeters.
The slots should be less than 0,3 mm above the fingerboard, if my memory serves me correctly (I'm on vacation, so the brain is more cut off than usual - even

)
Take it slow and easy, and good luck!
BTW: if you fail, a nut is fairly easy to replace....got my drift?