Some people reckon that spraying garlic water on the plants deters slugs (there’s a recipe for it in here: https://www.gardenersworld.com/how-to/grow-plants/gardening-with-a-clear-conscience/ ), but also sheeps wool (if it gets damp the slugs might settle underneath, so it’s worth checking for that if it’s been raining, but when it’s dry they don’t seem to like slithering over it), having an area ie. raised bed which you can put copper strips round. Also Stef has in the past recommended some stuff called strulch. You could also go out after dark and evict any slugs in the area to a different part of the garden. They will probably come back, but it might give you a bit of extra time. But I would water the plants early so that the soil isn’t damp around them in the evenings. Slugs like it a bit damp. Some people also use crushed egg shells (you might need quite a lot of that to make a thick enough area round each plant).
But, if I were you – and they are only plug plants – I would pot them up first to larger pots and grow them on a bit before putting them into the garden. Plug plants are so tiny, they make a bit of an easy meal.
Totally agree, slug pellets not a good idea.