We took a curtain rod, (the center piece of the kind that three slide
together make one with an adjustable length), and bend out the sides of
the "center piece" with a pair of pliers.  Then we screwed it to the bottom
of the front of the stove with sheet metal screws (you might have to drill
a couple of small holes.)  It is narrow enough that it still allows for
circulation under the stove, but not even the smallest ferret can't squeeze
under.
 
We keep the broom and dustpan between the fridge and wall, seems to deter
most from bothering to go back there.
 
The dishwasher goes all the way to the floor, and fits under the counter
snugly, no side gaps.
 
We have "childproof lock things" on the cabinet doors.
 
Luckily our house is fairly new, and there really aren't nooks and
crannies.  If I had a home that the kitchen couldn't be ferret proofed,
I would use gates to keep them out of the kitchen.
 
Anne
[Posted in FML issue 2929]