Mum - Here is how I sow potatoes using weed membrane.
Whatever you do don't cut the holes or the sheets as they will fray, I now use a soldering iron and melt/cut the sheets and the holes and they last longer see my old diary at
http://chat.allotment-garden.org/index.php?topic=100234.msg1354963#msg1354963Left = 2013 without the weed membrane using a hand Auger I use for sampling soils and short bore holes
Middle = 2014 with Weed membrane and I made the holes 100mm dia. as the Auger is 75mm dia
Right = the two different types of Auger head.
Bed/ sheets are 2.4m x 1.2m holes at 400mm in from each side on the 1.2m width then at 240mm centres
I also use a bulb planter to extract a core and transplant plants in place when using weed membrane. Take a look at my diary on here and you will see how I use them and how they frayed the first year.
The membrane reduces the weeds and keeps the moisture in. I've now added a X cuts so that I can add Pop bottle with holes made with mapping pins on the top that go in top first (upside down) into the ground and I cut the bottom off. Then I add more pop bottles with the bottoms off to extend the height as the plant grows, and water at depth.
The membrane means no building up as it keeps the light off the potatoes.
I'm currently growing green manure on the potato beds where I have harvested and once that's cut and dug in, the beds will be heavily watered and covered with a full membrane sheet for the winter only to be exposed to the world again a couple of weeks before we start again.
I also have sheets with planting patterns for Cauliflowers, Sprouts, Sweetcorn, and now French Beans and for Butter Nut Squash and Marrows, it's only carrots, parsnips, onions, spring onions and beetroots that I don't use Membrane to reduce the weeding.