Lay down a thick layer of CARDBOARD in your raised garden beds to kill the grass. It is perfectly safe to use and will fully decompose, but not before killing any grass below it. They’ll also provide compost and food for worms.
FInally I have something I can do with the 6' by 12' concrete pad in the middle of my yard. I can put 3 of these on it and rotate crops each year. I love these as they are self watering and high enough to give the rabbits a hard time.