Edit objects in frontend

[IamSAB]

I need some help regarding the editing of flex objects from the frontend. I really tried hard to find an answer to following question but failed:

• How create flex frontend form and populate it with object data. Here it states one could create custom forms, but how?
• How can I submit the form and process it? I seems this should be supported looking at the ObjectController. But how can I use this controller?
• Is it necessary to write a custom page type for the form or can I achieve everything with a proper flex configuration in the frontmatter and write some code behind the scenes listening to various events.

Flex objects seem very powerful, but a lot of features are not documented and hard to grasps when new to Grav. And looking through its source code to understand how things are done are tedious. I know it takes time, but a basic guide with different use cases for flex objects would be really helpful.