
IMHE, the only way that you can stop a dog chewing
anything when you are not present, is to physically remove them from it, ie, a crate, as bluebell said ;)
Why aren't you keen to reintroduce a crate? I know that some people and dogs don't get on with them but if they are used in the right way, for a minimum amount of time, they can be a godsend :)
I have only recently been using crates and this is the first house that we've had that hasn't looked like a domolition site :D My little darling is now 6 months old and from experience is still prone to the odd "kitchen lino rip" when my eye's off the ball which is why she still sleeps in her crate at night.......of her own volition as well which makes life easier for all of us :)