F2F
Having the nasty habit of not letting a puzzle go unsolved, I came up with a method to do what you were asking in a simple and interesting way…
I did a little something similar to your puzzle by doing a couple of passes on the design. Let me preface this by saying that I am using Corel VideoStudio Pro2 as my editor.
First pass
Using layers, I set up a white (or whatever color of choice, other than green, for the frame) as my primary set to full screen. Then layering green fields within the color field cropping them to give me my borders. I set them up on a time line for position and location change by changing box size, duration and such. Once I get the “frames” how I like it I then render this out. This becomes a template for the next pass.
Second Pass
I then pull in the rendered template as my primary and using simple chroma key, layer in my video clips. By changing my layer positions (this selects which is in front or behind the others) and clip durations (as those in front end their timeline, those behind fill in that now open space), and adjusting their sizes I end up with something that looks pretty much like the format of those you were pointing out.
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