not really, ill explain it in simple terms,
-you extract the skin of the destructable rock from the wc.mpq(just the name of the game's files)
-then you extract the skin of the blizzard cliffs(not blizzard as in snowstorm, but the company blizzard's premade skin)
-Find out what parts of the destructable's skin is where(like what parts of the skin show the sides, etc...)
-using what you learned above, cut and paste the blizzard cliff's skin parts into the correct areas on the skin of the rock destructable.
-after that, import your new modified rock destructable skin into the map and rename it to the file path of the original rock destructable's path.
-create a new destructable based off the "Invisable Platform" and change the model of that to the rock.
-congrats, you now have a perfectly good cliff!
P.S.- though i dont think this can be done instead with trrigers, it MIGHT be done with vjass, thoug i highly doubt it and i dont know vjass.
P.P.S.- If you dont understand, ill try to make an even MORE detailed tutorial using pictures, though that might take a while. Reply if you want me to make one more deatiled, or if this one is good enough.