Using Flox with cubed

[TomNicholas]

What would need to happen to use flox with cubed instead of dask?

(I see this question as part of fully solving https://github.com/pydata/xarray/issues/6807.)

In the code I see blockwise being used, but also dask.array.reductions._tree_reduce and custom HighLevelGraph objects being created. Is there any combination of arguments to flox that only uses blockwise? Could more of flox be made to work via the blockwise abstraction? Should we add ._tree_reduce to our list of useful computation patterns for chunked arrays that includes blockwise, map_blocks, and apply_gufunc?

Sorry if we already discussed this elsewhere.

EDIT: cc @tomwhite