The best practice for Flex PCB Design, when the circuit bend is unavoidable, is to keep the track work as gently curving as possible, using conical radius bends.

This goal could be reached both with Round Tracks plugins (being aware to highly discretize the curve) or even with real arcs, using the Arc footprint Wizard included in the tools.

Moreover near the connectors it is advisable to taper down from the pads. This can be achieved using the Taper footprint Wizard included in the tools.