How to lay out an extruded frame on a block?

Question

Layout

Good afternoon. During the layout process, the question arose: how to implement such a feature? I understand how to make an arrow - through pseudo-elements, but here's how to make such an "extrusion" effect, for the life of me I don't understand. A specific example is not needed, only a general concept through which all this is implemented or a direction in which to dig. Thank you very much for your help and your time