There's more than one way.
I've used lots of different kinds of scope protectors that I've seen on forums. From them I've developed one that I now use.
Start with a piece of an old intertube and a couple zip strips. I use the zip strips that are reusable.

Cut it to fit tight between the rings and cut a U notch for the scope adjustment knob. Punch holes for the zip strips.

It's simple to make and is easy to take off the scope and wash.

Works for me anyway.
Art