This uses hardboard (or masonite) and styrofoam for the form. I cut out a couple of masonite pieces for the two pools, and used flower arranging styrofoam cones for the rock in between. The styrofoam was cut with a knife to the desired shapes, and the edges roughed up with a fork to help it hold onto the wood putty in the next step. The cones were glued on the masonite with wood glue.

 This shows how the cones would fit together. I decided to make it in two parts, as it would be easier to get the wood putty on if I didn't have the masonite on both sides of what I was working on. I also could have done it as one piece and left the smaller end unattached until it was mostly covered with wood putty.

Coating it with wood putty was pretty straight forward. Any kind of topography I thought I'd get from my cuts in the foam was lost, but new topography formed from the wood putty.

After these layers were dried, I put the two ends together with some glue and used toothpicks for extra support. I poke holes into the foam with the tooth pick, then pull them out and put glue into the holes before reinserting the toothpicks. That may have been overkill considering the wood putty, but it turned out very strong so it was worth the extra effort.

I also put a rim of wood putty on the lower and upper pools (just lower seen in the photo).

After the two pieces were glued together, I filled the seam with more wood putty to make the transition flow better from the two parts.

After drying, I cut channels in the upper rim where the lava would pour out into the lower basin.

The wood putty was then sanded, and everything painted with the base color I've been using for my Hellscape rocks (Charcoal). This was allowed to dry.

 After drying, rocks were drybrushed with Iron Oxide. This is the same color scheme used in the rest of the Hellscape. Now for the lava!

The original plan for the falls was to pour out strips of Woodland scenics water mixed with red paint (the lava base color, as was described in previous Hellscape sections), peel them off when they were dried, and glue them to the channels cut in the top basin. However, the WS water did not peel off of the aluminum foil, and so the strips had to be cut with the aluminum foil still backing it. I decided with would probably provide more strength, and built this frame for painting the front and backs of the strips with more WS water mixed with red. The strips were hung from the frame with tacks, and painted with the lava base color. This made them fairly thick.

After drying, the strips were trimmed to fit into the top basin's channels, and glued into them with normal crazy glue. The bottoms of the strips were also positioned and glued down to the lower basin.

After the glue dried, more lava base was poured into the top basin to cover most of the evidence there that the strips were separate pieces. This took two layers, with the first mostly equaling the strips' thickness, and the second blending the strips with the fresher pool.

After the top dried, more lava base was pour into the lower pool. Unfortunately, I did not have a level table where I did this, and one side got a bit messed up. I eventually had to use three layers to try to recover, and there was still a large ripple. For larger pools, be sure the terrain is level!

I also put a couple of extra layers where the falls entered the lower pool. This camouflaged the shape of the cut ends, and gave it a bit of a bubbled up appearance. You'd expect some turbulence, after all.

After the lava base had dried, lava detail color was made by mixing Woodland Scenics Realistic Water with yellow acrylic paint, though less concentrated than the red was. This was dabbed with a brush onto the red, where it gave a fiery appearance to the lava. Extra yellow detail was added where the falls entered the lower pool, as hotter lava would be churned up there.