I am using nRF Connect SDK v2.2.0 with nRF52810 on a custom board.
We have included OTA updates in our project, and it works successfully and downloads the firmware via MQTT and writes it using developer.nordicsemi.com/.../dfu_target.html.
Because the internal flash nRF52810 is not enough for us, we want to use the external flash AT45DB0 to store the firmware image.
As an example I used tests\modules\mcuboot\external_flash.
As a result of the build, I get an error:

I made a child_image\boards .overlay file:
I made a child mcuboot.config file:
Added pm_static.yml file static partition to the root of the project:
I spent a lot of time to understand why it doesn't work. I hope you can help me.
I can provide you with the source files of my project if you need them.