I'm making some educated guesses on what the OP did, but a base like this is a lot easier than it looks.
The main parts are cork, glued together, painted black and dry brushed with shades of grey. Peronsally I try and ripup my cork by hand to give it a more natural appearence.
In various spots it looks like he glued on small pieces of rock and treated with the same paint as the cork. I typically use this
The grass can also be purchased. I use items like this.
Hope this helps, making bases is fun and adds a great layer to your models.