I used river (pea) gravel and took a pair of panty hose and cut off about six inches (the hose expands and lengthens) above the toe area. I then filled it with gravel and tied off the ends. I then cut off six more inches tied off the end, and filled it with gravel and tied off the other end. I put it over the lowest sections of the driftwood and once in the tank, scooped away the flourite, flattened the nylon filled gravel the best I could and then covered it.
You will do much of this by feel, as the water clouds quickly after disturbing the flourite.