Only flat linear sections of sheet metal can be used as the stationary base face for a flat pattern.
Fusion 360 sheet metal flat pattern.
To do that create the sheet metal part from scratch in fusion 360.
Go to modify flat pattern.
In this quick tutorial video synergis eds applications consultant dave breiner looks at the new bend feature within autodesk fusion 360 sheet metal.
Create a small flat tab somewhere on your design that can be cut off during manufacturing and use that as the stationary face for the flat pattern.
Link to vote for improved sheet metal tools in fusion.
Select the stationary face.
Sheet metal bodies with multiple radii curves or arcs in the sketch.
There was an unexpected problem with exporting the flat pattern as a dxf file.
An example of the procedure for a sat file is presented in the screencast below.