A bowl (unfired) is made on a potter's wheel. Creating an unfired bowl requires a minimum of level 8 Crafting and gives 18 experience. In order to make one, Clay must be used on a water source to be made into soft clay. Once the soft clay is made, you must use the soft clay with a potters wheel and select the bowl.
Potter's wheels can be found in Gunnarsgrunn (Barbarian Village), Crafting Guild, north-west corner of East Ardougne, Digsite, Draynor Village, and in Rellekka, kilns will also be found nearby the accompanying potter's wheels.
For the quest Dragon Slayer, an unfired bowl is required as one of four items in order to obtain Thalzar's map piece from the Oracle on Ice Mountain. The Grand Exchange may be used to buy items such as the unfired bowl.