Anyone make soap?

Have any of you made lye from scratch?
I'm planning on making soap from moose tallow, and getting the lye from poplar ashes, but just have a very sketchy recipe for how to actually make lye from ashes.

You soak the ashes in water I think, but it seems very hard to predict the strength of the result. Hard to know how much to use.

Yeah, I have a native recipe that outlines the general procedure but doesn't say anything about amounts. I guess it'll be trial and error