Yes, that's in the docs, but you need to mount the LED's first - then test them to make sure that they work and are solid before covering them with the chips. In a pinch if you get stuck, you can mount replacement LED's "surface mount" style on the pads. No one is going to see this from a distance of more than a foot anyway, so there's a workaround for burned out, or erroneously mounted LED's.
All in all though - time to make a s.m. version of this whole thing - Too bad the manufacturer has made the chip extinct - I like it a lot.