Raw materials are the part of stocks that have been purchased for further processing, but on which no work has yet been done.
The valuation of raw materials is more straightforward than that of work in progress. There is no question of cost allocation: raw materials cost what the supplier was paid for them, and this is the value used in the balance sheet.
This still leaves us with the same options as for any form of inventory: FIFO, LIFO, replacement cost, average cost, and specific cost.
The exception to this occurs when there is reason to believe that raw materials may be worth less than was paid for them, in which case they are valued at net realisable value — in the same as other elements of stocks in the same circumstances.