But isn't a bit of a pain to separate the top fraction (like the top layer holding the freebases) using an large separatory funnel? I personally find it quite messy and not as easy-as-advertised. I also get the impression that people often think that sep funnels will greatly ease their extractions without thinking too much about how they plan on using it or whether it will actually make things easier.
If your solvent rises to the top (naphthas, aromatics and terpene-based solvents) then siphoning off is far more practical in my opinion. A sep funnel will really not make things easier in this situation. Why?
1. As you remove the bottom basic aqueous layer with a view to keep the top (solvent) the basic aqueous layer will be smearing the sides of the sep funnel. In the end (and unless you take extra steps like adding more water to clean off the smears, then separate again etc, uuugh, the pain!) you will have a far more suboptimal and dirty separation than siphoning the top layer.
2. Moving around by transferring the basic layer does not sit well with my idea of safety. Really, why get into the situation of moving around from vessel to vessel a caustic solution? Safety-wise, makes little sense. Just leave it be in one constant container.
However, if the solvent sinks (like in halogenated solvents e.g. DCM) then the true potential of the sep funnel is realised.
I find that a small sep funnel (250-500ml) is excellent for salting naphthas, aromatics and terpene-based solvents. Instantly practical because in such cases the bottom aqueous layer with the salted alkaloids is collected. Cactus extraction definitely benefits from a small sep funnel to assist with the saltings, and for said job, no way a large sep funnel is necessary.