How to freely control each corner of VisualElement?

I need to do something similar to turning inwards, but I’m not sure what to call it exactly. In general, when using the usual UI toolkit styles, I don’t get the desired result. I don’t know how to make it work

Here’s what I need to do:
image
Maybe I should create a custom VisualElement, but I am not an expert in the UI toolkit, so I only use the built-in tools :man_shrugging: