I have decided on a combination of blue rug juniper and blue pacific juniper to cover a small embankment in front of my house.

I have already sprayed roundup and killed all of the grass. I really need to mulch because the dead grass will be unsightly in between the shrubs until they fill in.

I have a slight slope and don't want to use weed cloth or plastic as the mulch will slide off. Should I just mulch over the dead grass or put something down to prevent weeds before mulching? Burlap sacks or something that would prevent the mulch from washing away, or will I be okay with just mulch directly on the ground?