For the waterfall leg, I’m using Full Blind Multiple Splined joinery as described by Tage Frid.
I discovered this method by asking a question in a forum post here on LJ. Thanks to Woodendeavor and Randy-ATX for directing me this way. I purchased three of his books. This description is found on pp. 102ff of Tage Frid Teaches Woodworking, Book 1: Joinery
The joint looks like this:
The two biggest keys will be to cut the slab correctly and building the jig so the miters line up correctly.
I don’t know if you can read these well, but here are the directions for building the jig (in this case for the half-blind joints, but the jig is the same.
-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson