Specifying Project.toml when starting Julia repository with binder

Hey,
I want to set up some tutorials with mybinder. But my .ipynb and .toml files are not in the root of my repository.
Is there any possibility to start binder with a specified Project.toml from a subdirectory to avoid installing too many packages?

I already activated the right project manually in the notebook by running

using Pkg
Pkg.activate(path_to_project.toml)
Pkg.instantiate()

But this takes too much time because first all not needed packages from the Project.toml in the root are added.
I just found some older answers to this in here but no perfect solution.