Do the preparation as per a standard installation. Don’t lay the weed control material yet. Install the timber edging paying special attention to creating a sound supporting edge at the top of the slope.
Spread type 1 sub-base across the slope to a depth of 2 to 3-inches and press it down by hand. Be careful not to push it all down the slope. Apply a coating of granite dust to a depth of 1-inch.
Tamp the sub-base and granite dust down with a piece of heavy timber. Don’t use a Wacker plate on a slope. Fit the weed control membrane on top of the sub-base to help bind the aggregates.
Install the synthetic grass as normal nailing it to the edges.