The intent of Paste of Stickiness is to stick someone to what the Paste was stuck to. If someone applies it to the ground, and someone stands on it for more than 3 seconds as specified in the book, they should be stuck "to the ground" - think of the Paste as dripping down the blades of grass, sinking into the dirt, etc. to get a really good grip. The Paste cannot be broken/removed/moved by someone of normal strength lifting their leg.
-Bryan