Try ^stone$
Pretty sure that works in NEI; I don't know if AE will accept it.
If that doesn't work and you have a mod that adds storage barrels, like JABBA for instance, have your AE system fill the barrel with smooth stone and put the smooth stone barrels wherever you're most likely to need some smooth stone.
If you need it for recipes that require smooth stone in them, or for automating Botania, have it directly request it from the AE system, or have a recipe available that turns cobble into smooth stone in any mod furnace available to you.
If you don't want to go the barrels route but don't care about giving your smelting setup something to do whilst not processing ores, you could set it up so that it will fill a storage disk with smooth stone automatically for you, although preferably you should dedicate a setup just to fill smooth stone orders.
There are many ways to get AE to deliver any amount of smooth stone for your needs. Searching the internet may help!
Cheers ...
BrickVoid