Planting a Laurel hedge is generally straightforward but it is important to do the planting well as this will effect how quickly your hedge will grow.
1. Clear the area where you are going to plant the hedge
Remove any grass, weeds, brambles or other plants from the area where the hedge is going to be planted. You can spray with a glyphosate weedkiller such as Roundup or Bayer Glyphosate. Ideally, this needs to be done a couple of weeks before planting as glyphosate weedkillers take a little while to work. Having said that, as long as the weedkiller has dried on the grass or weeds (this normally takes about 6 hours in good conditions), it has no residual effect in the soil and so will not harm the roots of any hedging plants. Alternatively, you can remove the weeds with a garden fork or take off the turf with a spade. Discard or compost the turf, don't put it back after planting or grass will grow up through the bottom of the hedge and compete with the foliage of the hedge.
2. Dig the holes or trench
It is best to dig square holes about twice the width of the rootball. Dig the holes to the depth of the rootball plus an inch or two more. It is really important to break up the soil in the bottom of the hole to at least another spade/fork depth so the roots can get into the soil easily.
If you are planting 2ft (60cm) apart, it is probably worth digging a trench as it is easier to keep digging along rather than starting new holes. As above, make sure the soil in the bottom of the trench is broken up so the plant roots can get into the soil without a problem. If using a digger to dig the trench, then make sure the bottom of the trench is dug over to a depth of 12 inches (30cm). Diggers can compact and smooth over the bottom of the trench if you're not careful and this can result in the trench not draining when it rains heavily or the compacted soil layer can prevent the plant roots from getting into the ground.
If you have good quality soil (i.e. it breaks up easily) then you only need to add some controlled release feed (such as Osmocote) to the bottom of the hole. This will release feed over several months and give the plants a good start. If the soil is very heavy or very sandy, it is a good idea to add a loam-based compost (such as John Innes No.3 compost) or a good quality top soil to bottom of the hole to give the plant something better to root into. It is also worth adding controlled release feed.
If the soil is poor or difficult it is worth adding Rootgrow to the bottom of the hole as well as feed. Rootgrow is a friendly mycorrhizal fungi that works in symbiosis with the plant's roots to form a secondary root system that helps the plant get a good root system established.
The important point to note is that if the plant can get a root system into the soil quickly and easily, then it is much more likely to survive and will also grow and form a hedge quicker, so spending a little extra time on planting properly is essential for the long-term benefit of your laurel hedge.
3. Put the plant in the hole
Carefully place the plant in the hole. Make sure the top of the rootball is one or two inches below the top of the soil surface and not protruding above the top of the hole.
4. Fill the soil back into the hole
Shovel the soil back into the hole and firm with your heel around the sides to make sure the rootball is firmly placed in the soil.
5. Stake the plant
If the plant is more than 4ft (120cm) tall or in an windy position, you will need to stake your plants and tie them to the stake with a tree tie. This is to stop the plant rocking in the ground and breaking new roots as they are formed.
Stake the plant near the base of the trunk (approx 12 to 18 inches - 30-45cm - from the ground) with the stake driven in at a 45 degree angle. The end of the stake that is sticking out of the ground should be facing the prevailing wind so that when the wind blows, it blows the stake into the ground rather than out of the ground.