You didn’t think something so easy and simple could earn you more RS gold, but you can. It is just simply converting clay.
Source: runehq
Making Soft clay and get more RS gold
Converting clay into soft clay is a good way to make RS gold. Soft clay is a good demand because MEMBERS use soft clay to make teleportation tablets. Making soft clay takes time so most of the players instead buy at the Grand Exchange.
Making soft clay is just a simple process. Of course you can’t make soft clay without clay in your inventory. Be sure to mine some clay or buy it at the Grand Exchange. Buy as many as you can as long as you have enough RS gold.
Source: wikia
Once you purchased a lot of clay, head to the nearest fountain at the middle of Grand Exchange. At the fountain, you can use the clay on to the fountain. A new display will pop up; choose to make “All” soft clay. All the clay in your inventory will turn into soft clay. Once you process is complete, head to the Grand Exchange and sell the entire soft clay for RS gold.