If possible try not to place your vegetable patch close to anything that offers good cover for large snails and slugs.  While small slugs will happily live in your vegetable patch, especially if it is heavily mulched, large snails and slugs generally have to travel to it from nearby cover to feed each night, returning to their hiding places before the light of day.  This is especially so in the early Spring when there is usually no large plants in the vegetable beds to offer cover.

Shrubs, small trees, rock gardens and long grass against fences make ideal cover for such creatures. If possible use pre existing features such as concrete paths and brick walls as borders to your vegetable patch.  As well as offering little cover for large snails and slugs they also act as heat banks, which will raise the temperature of your vegetable beds.  Something that is very useful in early Spring.

While it is useful to make use of pre existing features to deter these pests this should not override the key factors listed on the Siting webpage.  Which are sunlight, shade and the distance from your kitchen.

Sometimes you cannot avoid placing your vegetable patch near good cover for large snails and slugs.  If this is the case then consider placing a gravel or even grass pathway between you and the cover, as even this small gap will act as a some deterrence.