How can I decide if I should place the conanfile.py in a subfolder like recipes/foo/conanfile.py, or if I should put it into the root folder of the repository?

What I have seen so far, is that if I have the conanfile.py in a separate folder, then I need to resort to custom configurations like explicitly setting the src_folder in cmake_layout`:

cmake_layout(self, src_folder="../../src")

or having to set the root explicitly:

self.folders.root = "../.."

Is that a good practice or does that indicate a problem in my conanfile?