Hi, I'll try to be useful for my first post at TYM
The B1,2, 212 works the way you want it to with a NJP starter. So to get there you could B1,2, Ice Blast (or anything leading up to a freeze), followed by NJP, B1,2, 212 Slide.
I hear you in that some can get a straight B1,2, 212, Slide... notably in online matches... but that happens only when the opponent isn't holding the block button.