Unlike "Single Slippery Block", this one, you don't need an anti-slippery block placed above the slippery block for a workaround prevention. It also has proper slippery corners without making the whole level slippery. It requires Uberasm tool.
If you use these blocks in tandem with GHB's pipes in an SA-1 ROM, the pipes'll act weird even if there's no free RAM conflict between them. To fix that, just go to SlipperyDefines.asm and change the $7F in '!Freeram_SpriteSlip' and '!Freeram_SpriteSlipFlag' to $41. Make sure both copies of that file are up to date, of course! It took me many months starting from the beginning of this year to figure this out.