When starting off on a tapered hill, the materials you would need involve Styrofoam, a pack of knives, and a bit of effort. Cut out a large layer from the Styrofoam, this is probably going to be the largest layer.
Cut out additional layers, specifying the height you desire. Each layer that is cut out will be slightly smaller than the previous one. If you want to recreate the texture of a cliff, then line up the layers vertically or as close as possible. Using your retractable knife, taper the edges by cutting and extending the foam. Focus on a single layer, then work your way from top to bottom. Make sure the tapered cuts are lined up and are close to the edges.
To make the base, cut out a layer from the Styrofoam using your knife. Taper the edges and sand the base out, this is also where the hill will be placed at. Because there is a risk of inhaling toxic materials during this part, make sure you are wearing a mask.
The next step is to cut some pieces of cork bark, this will provide the face for the cliff. Most pet stores have sheets of cork in stock. Carve the edges and back of the chunks until you have a close fit. It doesn’t have to be perfect, avoid having any deep gaps larger than 5-10mm. Now glue everything together, and let it dry for 24 hours. If you want to save time, you can use a glue gun. However, be sure to note which ones can melt Styrofoam.
Now sand the Styrofoam down, making sure the taper is at its smoothest. The more precise you can do this, the better, but 100 percent perfection isn’t necessary. Grab a bucket of filler and start filing any gaps. Before you start the next step, make sure the filler is completely dry and you have your facemask on. Once this is done, sand everything down with sandpaper.
To make the ground cover, place some large cork boulders at the face of the cliff. You can use undiluted PVA to secure them into place. For rocky terrain, you can use a coarse gravel or sand mix. The choice of terrain however, is yours, so the step is left up to you.