Hi fuzz & Tom,
I've made several of these panels,
We call them "Fielded and Shaped" panels, they are commonly used on; George 1, Furniture. (1725) In Oak.
"Dresser". I have made oak L shaped, hot water cabinets. To match an oak "Cloths Press".
As in their day's. (It would be all done by hand)
So I have always made a scratch block to the same angle as the required shape.
Then used the electric router (all around the panel, to take out the thick in wood in steps), but leaving it over sized? Then finished it with scratch block.
This is easily made just take a: 6"X 2"X1" piece of scarp timber, cut a "Set Square"shape.this is to hang over the panel edge,( just as in feature" Scratch box" 09 Jounal. (Fig 7, middle) just cut down the centre of the 1"thin end. to receive, a "Angled" scraper blade, (cut from an old discarded saw blade) a woodscrew each side of blade, to secure it.
Then just work around the panel, hold as you would a "Marking" gauge, working "Backwards and Forwards", till the block is touching the panel surface, Then a sharp chisel to clean into the sharp corners this gives the correct hand finish, to the piece.
Joseph Hemingway