After 3 days of using my Vintage Re-issue Sling, trying it both as a backpack and cross-body, I realised it gets a bit tiresome retrieving my things. I tried just slinging it over my shoulder as well, but it slips off after a while. However, I wasn't ready to give up on this bag (even though the feeling of regret was slowly creeping in.)
So I was experimenting with the straps and found a simple way to convert it into a bucket bag! Instead of using the straps backpack style (it's original purpose), I pulled out the straps from the left and right side. This pulls in the straps from the back (the backpack straps disappearing), creating 2 shoulder straps.
Now it sits comfortably on my shoulder and doesn't slip off, plus it's so easy to get in and out of the bag. I've always wanted a bucket bag as well, so I guess I finally got my wish.