"Undevised" refers to something that has not been planned or created, but there are many antonyms that describe the opposite. For example, "planned," "designed," "created," "formulated," "generated," "crafted," and "envisioned" all describe an intentional act of thought and preparation. "Invented," "innovated," "conceived," and "devised" suggest a new idea or solution has been thought up, whereas "crafted" suggests careful attention and skill to make something. "Formulated" suggests a systematic process of creating a plan, and "generated" suggests the act of producing and bringing something into existence. In short, there are many words to describe the opposite of un-devised, all of which suggest intention, thought, and careful planning.