cut and dried

adjective
  1. 1

    Simple, straightforward, clear, or certain.

    โ€œTake care when guessing, since problems do not always have cut-and-dried answers.โ€

  2. 2

    Decided, not open to change.

  3. 3

    Lacking freshness or spontaneity.

Source: https://en.wiktionary.org/wiki/cut%20and%20dried