Here is what we have to start with. 1 thing to remember is don't do too large an area otherwise you risk the glue setting when you are not ready for it to.

Now, with a flat flexable stick, I used a piece of .040 styrene, spread out the glue and get the best coverage you can. Add more glue as needed.

Here, I lay down some grass and earth go use as an undercoat. Spread as much or as little as you like.

Now, pour out the sand. Cover all the glue then pat down the sand to get a good secure hold with the glue. Don't worry if the sand comes up, you can always pour more.

Here you can see glue is showing through after I patted the sand down. Again, don't worry, just add more sand or as I did, put grass and earth there.

As you can see here, where I had glue showing, I poured some grass there. Even in the desert, grass can grow. Or add more sand.

After the glue has a chance to set up, about 30 minutes or so, just vacuum up the loose material. If you have any bare spots, just repeat fill it in.

From a back shot, you can see there is no sand where my building is to be and the grass shows up.

A closer shot with my building added. Now all you have to do is add some brush, or foliage of your choice.

Here you can see the finished project from another area on my layout. Here, I have more grass than in the other spot.