procedural texture mapping? (I think thats the correct term)

How to do this?

preferably with a blend in between the grass and cliff textures.

I tried searching for answers but I think I am using the wrong keywords to begin with so some help would be greatly appreciated!

I just need something of a time saver so I don't have to do that to every piece of floor in the game.

 

Look into vertex blend shading. A good way to do this would be to tell the shader to use a different part of the texture map based on blended vertex colors. Then just color your cube top vertexes to "paint" the grass.