I know this is off topic but it's not every day you live during a pandemic.
I found this technique on the internet but there was no way to fasten it behind your head. The hair ties were not connected and I just so happen to remember how to bind them so I made this video of them linked together. It can be a little tight so try and stretch the bands before hand so they don't break. I had to film this one handed because I don't have a camera stand but the basic information gets across.
Here's what the end result should look like. Tuck the ends of the bandana flat. These will rest against your face.
This is what it will look like on. Stay safe everyone!