The single biggest change is not a remedy at all: plant out later and bigger.
A slug can destroy a seedling in one night because the whole plant is within reach and there is very little of it. The same variety planted out three weeks later, twice the size and with a tougher stem, gets chewed and survives. It is the same slug population and a completely different outcome.
So:
Pot on rather than planting out at the first opportunity. The impatience is understandable and it is what costs you the tray.
Harden off properly so the plants are not soft when they go in. Soft growth is the preferred food.
Plant out on a dry spell if you can choose. A warm wet evening is a slug convention.
Do not plant out everything at once. Half now, half in a fortnight. That way one bad night costs you half a tray rather than a season.
Beans and courgettes in particular are worth growing to a decent size in pots. Lettuce is genuinely hard because it never gets tough, and for lettuce the physical barriers and the trapping matter more.
On the remedies, the honest ranking is below, but do this first: it changes the size of the problem rather than fighting it.