Where should I place a stove master switch on an island?
You'll want to place the switch in a convenient accessible location, where it will be out of the way but still usable.  Without some type of plans/drawings/pictures of the island, the answer will have to be fairly generic.

Do Not:


Do Not place the switch where liquid is likely to be spilled on it.
Do Not place the switch where children can easily access it.
Do Not place the switch where it could be mistakenly toggled.
Do Not place the switch inside a cabinet or drawer.
Do Not place the switch where you will have to lean over (a presumably) hot stove.
Do Not place the switch where it could easily be confused with a light switch.


Do


Do place the switch where it can easily be reached.
Do place the switch near the stove (within arms reach preferably).
Do place the switch in an obvious easily visible location.
Do use a protective cover plate to protect against accidental toggle (by yourself/children/pets) Not a locking cover, you want to be able to access it in case of emergency.