The first step is to shape the soil underneath, to get the basic shape of a riverbed.
Step 1: Lay Weed Cloth
Lay weed cloth over the soil. This will prevent weeds in the soil from sprouting up through the rocks, as well as prevent seeds that blow in the wind from landing and rooting in your stream bed.
Step 2: Lay Large Rocks to Shape the Stream.
The shape of the stream bed itself will be lined with rocks.
Step 3: Add Small Rocks and Gravel
Lay small rocks and gravel over the big rocks, filling in between them.
Step 4: Add Wood Chips
Add wood chips at the edge of the stream bed, working your way out.