A few simple directions
Michael Pilarski, Friends of the Trees Society (2/3/03 edition)
The most effective sheet mulches are roundish in outline and at least 10 feet or more in diameter to minimize edge which can be invaded by rhizomatous weeds.
1). First chop down existing vegetation as close to the ground as feasible. Leave the chopped material as the first layer.
2) Plant any trees or shrubs desired (if any) in the area to be sheet mulched.
3) Water thoroughly unless the ground is moist from rain or winter melt-off.
4) Spread layer of rich material such as manure, compost or mushroom compost, lawn clippings, fresh green leafy matter,
5) A good addition if available is to add trace mineral rock dusts such as rock phosphate, limestone, dolomite, greensand or humates depending on the soil.
6) Add handfuls of red wiggler worm inoculum (contains eggs as well as actual worms) at regular intervals. Not entirely necessary but they help break down the lower layers of the sheet mulch faster.
7) Cardboard layer. 2 to 3 layers thick, overlapped like shingles. Full coverage. Pull the cardboard within a few inches of any tree stems which have been planted.
8) Chip layer. Broken down is better then fresh material but both will do. Deciduous trees are better than coniferous trees but both will do. Biomass from less polluted areas are preferable than from more polluted sources. Leaves, needles, twigs, and bark are better than the actual woody trunk chips. The finer the grind the better. Use whatever you can get, as long as it doesn’t have weed seeds in it.
9) Poke planting holes all the way through the sheet mulch with a heavy steel bar or a pick. Make a planting pocket in the hole and fill it with some good soil and then transplant herb plants or vegetable starts or flowers that you wish to plant. Water in thoroughly and remulch up to their stems.
10) Monitor the planting and pull the occasional weed which pokes its head up through planting holes, or around trees. After a few months the cardboard will decay to the point where weeds will gradually begin to emerge though the sheet mulch. It is easy to pull these shoots out if monitored frequently. The mulch can be renewed once or twice a year to maintain its effectiveness.