Ref/Inspiration:
Instructor is absolutely right about getting your frame set up from the start and ensuring items are good before applying modifiers. I love the idea of using the plane to create the frame and I can see many other uses in the future. I started off with the plan and extruded to dimensions I wanted, then started applying joins and subdivisions to make like an “origami” of my frame then used the location transforms to push the vertices in and added some beveling .
Closer look with cuts