I would like to introduce to you a new and improved IMHO method for attaching grass to the base. It is called...get ready for this...WHITE GLUE method. Simply put you cut a clump of tall grass, dip one end (the one you would normally shove into a whole) in white glue (not too much just enough to keep all the grass blades together and to give it some adhesion) and stick it onto your base. Once the clump is on the base you can but don't have to separate the blades touching the ground a bit to give it an illusion of grass coming out of the dirt in several places. Repeat this process as many more times as needed to cover up the base. Advantage of using white glue is that it dries clear so it is basically invisible after the dio is completed. I used this technique in my Ruined Farm feature.

Results are very realistic.