Learn it at the Level 2 workbench and the rest is gathering. The bill leans on wood, 600 of it, more than the stones, and the furnace burns plenty more once it is lit. So make the wood run for the build and for the first night's fire one trip, not two.
The fuel is the slow part: 19 crafts of low grade fuel fill most of the bench time and eat a good pile of animal fat. Hand-crafting is still right for one furnace. A small oil refinery costs several times this fuel to build, so it pays only once crude oil keeps coming in.
Watch out
Don't feed your small furnaces to the recycler to pay for this one. It returns about half of what went in, and a second fire for small batches is worth keeping. A plain furnace is a default craft you would only rebuild later.
Own the industrial skin? The Large Industrial Furnace comes out of this exact craft, with nothing extra to farm.
