Mountain Laurel, like their kin Rhododendrons and Azaleas prefer a soil well endowed with organic matter that is evenly moist but well drained. They do not grow well in heavy clay soils. With several to plant you will need to amend the whole planting area before planting and that should be done several months before planting. Soil pH should be in the 5.0 range, so you will need to make some adjustment to that soil.

Several years back, in preparation for planting some Blueberries I
mixed a bale (3.8 cubic feet) of peat moss in a bed that was 4 x 4 and had a soil pH of 5.7 (Blueberries prefer a lower soil pH like 4.5) and a year later that soil was retested at a soil pH of 7.2, indicating that you may need something more than Peat Moss to lower that soils pH.

In addition to a good soil test these simple soil tests may be of some help as well.

1) Soil test for organic material. From that soil sample put enough of the rest to make a 4 inch level in a clear 1-quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. For example, a good loam will have
about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of
silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%)
of organic matter on the top.

2) Drainage. Dig a hole 1-foot square and 1 foot deep and fill that with
water. After that water drains away refill the hole with more water and time
how long it takes that to drain away. Anything less than 2 hours and your soil
drains’ too quickly and needs more organic matter to slow that drainage down.
Anything over 6 hours and the soil drains too slowly and needs lots of organic
matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a
finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria
will be and the nicer your soil will smell, to a point. Too much organic matter can be bad as well.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

Ignore the above........mountain laurel do not require excessively acidic soil. They will grow perfectly well with a pH of 6.0. If you already grow rhodies and azaleas, then the laurels will do just fine.

Amending individual planting holes, especially in clay soils, has been proven to be detrimental to the proper establishment of woody plants. As with many other Ericaceous plants, the laurels have a very shallow root system, so plant high in a wide, shallowly dished planting hole. Backfill only with any removed soil. You could mulch with peat after planting however it has a tendency to dry out when exposed and is then very difficult to rewet. It would be better to use a light mulch of bark or wood chips.

From the article linked here from Clemson, " Mountain-laurels prefer acid soils with a pH of 5.0 to 5.5. While many of the Upstate soils in South Carolina are within this range, it is important that these acid-loving shrubs are not planted in areas that have been recently limed."

http://www.clemson.edu/extension/hgic/hot_topics/2010/05mt_laurel.html

I love a good pHissing match! LOL

They grow perfectly well here in the PNW with a soil pH in the 6.0 to 6.5 range, as do rhododendrons (native to this area), azaleas, camellias, blueberries and virtually all other Ericaceous plants. The need for a highly acidic soil is generally overstated.