Here are the first few steps in turning all my blowfish sneakers into slides so they don't rub my heels into meat and I can actually wear them.
I will add posts with photos of the steps as comments to this post creating a thread instead of separate posts so it's easier to follow.
I first draw a curved pencil line from the side of the tongue on each side stopping approximately 1cm from the beginning of the side sole. You'll understand why shortly.