What is the recommended way to create a CustomField for Joomla 5 with a custom/own FormField?

[astridx]

What is the recommended way to create a CustomField for Joomla 5 with a custom/own FormField?

My attempts so far have ended in code that does not load the form field.

What am I doing wrong or how should I do this?

[Fedik]

For namespaced field you need to use FormHelper::addFieldPrefix() to register your namespace in the form, instead of FormHelper::addFieldPath().
Example FormHelper::addFieldPrefix('Foo\Bar') for field Foo\Bar\BeerField