I had been using a store bought poly-vinyl cord as a strap for my Get up and go go sling bag. But the ends of the cord were fraying so I decided to sew a long thin strap to replace it.
Here's how I did it if you don't already know how. First fold along the length to get about 30". You'll end up with 60". For my height 166cm (around 5' 5"), this strap is pretty long. But I like the bag to hang low, below my hip.
Use an iron to get the crease!
Is this how you sew a long thin strap? The magic is in the ironing.