I needed to mount a standard flight controller on a plane and an old F450 frame which don't have the normal mounting holes you'd find in modern mini-quads. Both of the models had flat bases, so I designed a simple mount which you could attach with a bit of double-sided foam tape (or similar) and then pop in a few risers and you can mount your flight controller. The idea here is that if you want to create a stack you can keep adding extra boards and risers.