Cut copper foil glued on non-adhesive polyimide foil, after removing obsolete copper by hand

Cut solder mask out of adhesive polyimide foil

KiCad export/gerber options for edge-cuts

Options for bottom layers: Turn off drill marks

Silhouette Studio: A small red square for testing position is useful

Select merge

Select edge cuts layer

View after merge

Select all objects and group

objects from edge cuts are one object now

change the colour for edge cuts: This is important for seperate cutting settings

Select merge again

Select your bottom layer

leave the colour set to black

Select all objects and flip horizontally, because the FPC _bottom_ is being cut

Flipped view

Select all objects to move

Setup material and test with the red square

If position is OK, select the bottom copper layer

Last step: Cut dimension and holes