Choose a level spot for your lasagna garden, as well as the right sun or shade environment for what you want to grow. Remove anything that might make bumps under the cardboard.
Prepare the cardboard by removing any tape or staples. Lay it down and add your first soil layer, followed by layers of dried leaves, grass, newspaper, or compost, and more soil.
Level out the surface and make sure the soil is deep enough for the roots of your plants. Shallow-rooted plants work better for this type of garden than plants with deep tap roots.
Add some kind of edging to keep the soil in one place, like bricks, stones, or cinder blocks. After you add plants, add enough soil to cover the roots to the proper depth.
If you see any weeds poking through around the edges, remove them by digging them out by the roots—pulling them may leave all or part of the root intact.