The modern way of making jigs is named CNC.
The lower part of the "Bonnet-Top High Chest" stands on four cabriole legs. The thinnest part of the legs is about 0.5mm so a little testing has to be done.
This is the screen from the computer that controls my small cnc-miller.
The drawing of the leg is first scanned into a CAD program and the contour is traced. Then the CAD-drawing is transformed into codes understood by the CNC-miller by another program.
Here the first side is milled out. The large parts at the ends is later used for holding the leg sqare when cutting the other side.
To ensure excact reference this pocket is milled in a piece of MDF.
After the first cut the leg is rotated 90 degrees and placed into the pocket.
And secured with holddown clamps. (the mdf is mounted on the millingtable with double faced carpet tape.)
Then second side is milled out.
And the leg is ready for next step.
CNC is fun and a great help but you still have to understand how a piece of furniture is made.