Strip Tube technique would be your easiest way.

If doing it with charm squares, using your pink/green example ... sew a green and pink together to make 2 HSTs. Then on the green side, sew a piece of the pink on, in snowball fashion. You could probably get four of those corner pieces from one charm square.

Why couldn't you just cut the corner off, sew a strip on, then sew the cut off corner on, then square it up. There would be some waste, but not that much.

There is also a book from Anita Grossman (I forget her married name) where she demonstrates cutting a block very much like the one you showed. I think the complete title is Rotatry Cutting Revolution. I have it at home - borrowed from the library - but am going to put it on my Christmas list. Interesting book.

blocks are neat.

The center strips you would cut out of each of the charm squares can be used in another block. (I have shown this in the 3 sets of blocks to left of the original block.) They will be a bit narrower, but very usuable.
You could also add scraps to those secondary blocks if you wish to spice up the centers a bit, or rotate them to the outside corners.

I will add the templates for these blocks. Edited*** These will all finish at 4"

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The pattern formed on the left is on Missouri Star Quilts tutorials for FREE -

It also looks kinda like the Tube block. Try looking for a tutorial. It is a neat way to do these kinds of blocks.

Here are the templates for each of the blocks mentioned above