Start out by visiting Doric at his house that is just off the road outside of the east gate to Taverly. The location is shown in the screenshot below. (Click any image for a larger view.)

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Talk to Doric, and he’ll ask for your help in obtaining some supplies. Specifically, he’ll ask for 6 clay, 4 copper ore, and 2 iron ore.

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You don’t have to mine these items yourself, but you can save a bit of money if you do. If you do decide to mine the clay and ore, it doesn’t matter which mine you use so you can plan ahead and just bring the items with you when you go to first visit Doric. Otherwise, there are several mines close by that have the required materials – the one in the Dwarven Mine to the east of Doric’s house and the one south of Falador near Rimmington are probably the closest.
If you decide to buy the items instead, you can get them from the Grand Exchange in Varrock. You can also find the ores in Drogo’s Mining Emporium located in the Dwarven Mine, but be prepared to spend more money if you purchase them there. Plus, the shop may be out of stock if no one has sold anything there recently.
Once you have the requested items, return them to Doric to complete the quest.