removing slugs has I think been done to death.
'no chemical' method (that is, no chemical in the soil)
- go down with a torch and pick off by hand. Best way involves getting your kids if you have any to pick them and pay per slimy body
- sprinkle oats around plants, they prefer oats and get fat/dehydrated
- beer traps (that's plastic pots buried into the ground, an inch or so protuding so beetles don't fall in and filled with beer)
- nematodes (expensive)
- add ducks to your veg patch
Tips:
- Water during morning (not night)
- dispatch any you find or relocate to compost heap
- build a pond and attract frogs/toads
- get a hedgehog nesting box and cross fingers for a hedgehog (they'll absolutely destroy the slug population)