Sheet composting or sheet mulch, is known as "lasagna" composting, after the popular Italian dish, for the way compost materials are spread directly on the soil in thin layers, like a great big pan of, well, lasagna. According to Patricia Lanza, author of "Lasagna Gardening," one of the main benefits of this composting style is it builds up the level of your soil, which allows you to create your compost in just about any location, without having to worry about the quality of the soil underneath your lasagna compost.
Select an area to lay out your lasagna compost, ideally a large, flat, well-draining location; it can be as large as you want, but try not to make it any smaller than 3- by 3-feet unless you enclose it in a frame. Cut any grass that will be under the compost location with your lawn mower, using the shortest setting to get rid of as much plant growth as possible. Mark the corners of your lasagna compost area with wooden stakes hammered into the ground; run a taut string between the stakes to mark the perimeter of your compost area.
Cover the entire ground within the marked area with four to five layers of old newspaper. Overlap the edges of the newspaper to discourage weed and grass growth. Spray the newspaper gently with your garden hose until it is thoroughly wet.
Spread a 2- to 3-inch layer of carbon-rich organic waste across the entire surface of the wet newspaper. Use dry materials to provide the carbon in your lasagna compost, including easy-to-find materials such as dead leaves, straw, old hay, shredded newspaper and cardboard. Dampen the waste with your garden hose; ideally, it should be about as moist as a wrung-out sponge.
Top the dry, carbon waste with an equal layer of finely chopped nitrogen-rich material. Ideal nitrogen-rich materials are moist and green, including materials such as cow or horse manure, grass clippings, vegetable waste and fruit scraps. Alternate the two layers of waste repeatedly, until your lasagna compost is between 18 and 36 inches in height. End with a carbon layer to discourage fly populations, which like to lay their eggs in rich nitrogen scraps.
Leave the lasagna compost bed alone to compost, allowing six months or more for the organic waste to break down to the point of being unrecognizable. Over time, the bed should decrease in height by about half and the organic waste should become crumbly and brown. Spread a 2- to 3-inch layer of plain topsoil over the mature lasagna compost to plant seeds or new seedlings directly into the nutrient-rich finished compost.