Craft Raw Materials
That's what adventurers call it; normal folks call this mining or logging.
Ask the DM if this is acceptable first, but the argument goes, though the game doesn't say raw materials can be crafted, raw materials must come from somewhere, and scrounging in the wilderness is as good a place as any to get them. All it takes is time.
The Pathfinder Craft skill says
- Find the item's price in silver pieces (1 gp = 10 sp).
- Find the item's DC from Table: Craft Skills.
- Pay 1/3 of the item's price for the raw material cost.
- Make an appropriate Craft check representing one week's worth of work. If the check succeeds, multiply your check result by the DC. If the result × the DC equals the price of the item in sp, then you have completed the item. (If the result × the DC equals double or triple the price of the item in silver pieces, then you've completed the task in one-half or one-third of the time. Other multiples of the DC reduce the time in the same manner.) If the result × the DC doesn't equal the price, then it represents the progress you've made this week. Record the result and make a new Craft check for the next week. Each week, you make more progress until your total reaches the price of the item in silver pieces.
If you fail a check by 4 or less, you make no progress this week. If you fail by 5 or more, you ruin half the raw materials and have to pay half the original raw material cost again.
Progress by the Day: You can make checks by the day instead of by the week. In this case your progress (check result × DC) should be divided by the number of days in a week.
Thus items costing less than 3 sp consume raw materials costing 0 sp. So the character crafts raw materials 2 sp at a time by spending 0 sp. The DM must determine the DC for crafting raw materials, but a reasonable house rule simply makes the DC equal to the DC of crafting the actual item (because were it easier folks wouldn't buy raw materials).
Gulliver Robinson's ship sinks and he washes up on a deserted island. After a few years, he realizes he'd like not to be trapped on a deserted island any longer. He wants to craft a
rowboat. A rowboat costs 50 gp. The DM determines that a rowboat is a typical item as per the Craft skill, but as the island is deserted (except for Gulliver Robinson, obviously), no one is available to sell him raw materials. He must make his own.
Gulliver Robinson's tracking his progress by the day. He needs to craft the raw materials for his rowboat first. He spends 1 day trying to gather 2 sp of raw materials. He is saddled with improvised tools and but his Intelligence 14 gives him a Craft (shipbuilding) skill bonus of +2. He takes 10 on his Craft (shipbuilding) checks, as 10 guarantees success.
He spends day 1 taking to to make 1 Craft (shipbuilding) check. He spends 0 sp to purchase raw materials. He takes 10 on his Craft (shipbuilding) check. He multiplies his check result (10) by the check's DC (10) to get 100 and divides that 100 by 7 for progress by the day for 14 sp, so Gulliver Robinson can make 8 Craft (shipbuilding) checks per day, making 2 sp of raw materials each check, therefore making 16 sp of raw materials per day.
It'll take about 11 days to craft the raw materials for a rowboat, whose raw materials cost 166 sp.
(By the way, if Gulliver Robinson takes 10 on his Craft (shipbuilding) checks to craft the rowboat he'll be done in 5 weeks.)