Make yourself a small pond, the frogs will eat them.
Adopt a hedgehog from your local R.S.P.C A they are always looking for people who have secure gardens for blind or injerd.
I have enormous quantities of slugs and so I plant plants that the slugs will not affect too much. I know that I cannot hope to dent the slug population - even by encouraging blackbirds which is my prefered option. When I love a plant that is slug susceptible like asters I spend a lot of time putting crushed eggshell round them and there is an equivalent rock you can get from the garden centre. Not perfect but helps. Pots help too - but slugs can climb.
I have occasionally seen a hedgehog in our garden, but not for three or four years now. How can one encourage them to hang around? Don't want to leave out food, as we also have urban foxes, numberless local cats and the dreaded rats!
I didn't know that frogs don't eat 'large slugs' hopefully the frogs won't allow them to get large. I live of clay land and when I came here 30yrs ago I used to fill buckets of those 'orrible big black ones. since making two fairly large ponds I hardly ever see one. I suppose it could be coincidence or some other reason but I'm happy with my ponds.
I agree with Ron - I get less slugs since the ponds - perhaps the birds come to drink and then stay for a snack?