Just stand it somewhere handy. I have a little one on the side in my kitchen and take it with me when camping. It hooks over the side of my camp kitchen by it's handle so I can grab it quickly if I need it.
Just have to remember to read the instructions occasionally to remind myself how to use it if I ever do need it quickly. Not much point standing there as the flames get higher while you read the instructions!
I've actually seen one attached to the outside frame of a caravan with a luggage strap. Owner says he does that when he arrives at site as part of set-up. Reason ?
Most of the time a fire will need to be extinguished because you never noticed something, ususally because you're sat outside. Secondly it means if he's not around someone else might be able to do something if they spot a fire.
I've decided not to mount it -mainly due to it being a fairly new van. In future I'm going to put it under my steps - out of the way but you can still see it and grab it quickly. Also going to invest in a fire bucket for peace of mind, as well as the fact we plan to rally this year and facilities i.e. fire points can be minimal.
Keep one of mine near the cooker (thats most likely where a fire would be).And one in the sleeping area....dont fancy my chances getting out of a burning sleeping pod