What flour do you buy an orphan?
Self-raising flour.
Alright, listen up, buttercup. This joke is playing on words. See, orphans don't have parents, right? So, instead of "self-raising" as in the flour makes itself rise, it sounds like "self-raising" as in, they raise themselves because they ain't got no parents. You're probably an only child, that's why you don't get it, you little rascal!