This bracket is for adapting the Mellow FlyMini-AB board to the Voron 0.1. It incorporates the stock design and all you have to replace is the existing backplate behind the extruder motor.
This design does not have strain relief for the Microfit 3.0, I didn't see the purpose as I didn't have much strain in my experience.
Backmost cover can be found here:
https://github.com/christophmuellerorg/voron_0_pancake_board/blob/master/stl/cover.stl
The author hasn't provided the model origin yet.