The corners of this block, F-11, as Jane Stickle pieced them, are very complicated. I just appliqued on the green pieces.
Now: if I am matching Jane I would put white fabric behind the block, and cut away the green fabric in a similar shape to reveal the white (reverse applique). Complicated and fussy. I can stop here, but I think I will just applique on the white pieces. And once you do one, you have to do all four.