We have plain old grass
The rocks or pebbles aren't so good because occasionally a basset may take a liking to eating them. Mine eat the mulching so we use very little. I have a separate dog run- it opens with a doggie door into a tiled kitchen. The dog run is fenced apart from the rest of the yard- They are able to go in a and out into a safe enclosed play area just for hounds- I do have a few plants like sweet broom that are behind a little gardening fence- it keeps the air smelling pretty but very little else... anything else in the run- trees included- gets gnawed upon!