ALL of the flash arrows on the picture you posted can be accomplished using the current flash, except two:
- The arrow going down into baron pit. To accomplish this you have to flash diagonally.
- The arrow going up from the brush towards mid tower. Again, if you flash diagonally you can also fix this.
After tons of experimentation, here's what I came up with:
All the lines I've drawn are what I deem the "difficult" places where you can flash over. There are a lot more obvious places that I haven't put here that I thought were obvious or trivial, including many of the arrows on the picture you posted. There are also definitely some "difficult" lines I haven't drawn - if you find some crazy ones, let me know!
I tried to maximize the distance you travel in each location, unless for some reason it seems stupid that anyone would want to be flashing in that direction. However, I'm sure many of these aren't perfectly optimal. They're also not pixel perfect, but should be mostly accurate. If you can't seem to carry one out, feel free to message me and I will try give you suggestions. Also, if you want to suggest another spot, or just have questions in general, you may message me as well.
Hope this helps!