Since most of my camera mounts are adjustable, I had a little trouble setting the exact angle and keeping it consistent across multiple drones. The trick with Betaflight and reading the angle is nice, but with two hands it can be difficult.

So I designed a very simple ramp with a defined angle. The drone is placed on the ramp and then you can freely adjust the camera very precisely. It just needs to be horizontal and looking straight ahead. To be even more precise, you can turn on the drone and use your goggles to check that it is horizontal.

The ramp is angled at the top. Place the longer side on the build plate (of course; just to make sure it is not overlooked). The stands may be a bit too tight or too wide, depending on the filament and settings. Use paper or glue if it's not tight enough.

To really make sure nothing moves when adjusting, I use some electrical tape to secure the ramp to the table. Otherwise it might move if you accidentally touch something.

I added the STEP files, so feel free to adjust. I can also add lower angled ramps. Hope it helps as much as it helped me.