adding a custom cave layer to terrain gen

Im making a noise settings file for a custom dimension focused around caves (using misode to make and visualize it lol) and im wondering, out of all the different operators and noise functions, whats the right workflow for adding cave noise to a specific layer of the world?
My end goal is to have a dedicated y level that consists entirely of a network of underground rivers. its probably going to be a lot more complicated than i think lol but thanks for any pointers!