Measure the area you want the sofa to be. Transfer the measurements to a piece of paper and sketch the design you would like to make.
Place hay bales, stacked in rows, to make the base of the sofa. To make pieces that are smaller than a bale of hay -- such as the back -- lay out burlap and open a bale of hay. Place the hay on the mesh and continue adding hay until the length is reached. Next, pile hay about 10 times higher than needed and wrap the mesh around the pile of hay tightly twice. Secure the mesh with twine when it is compacted to the correct height and depth.
Stand the mesh-wrapped hay behind the base of the sofa and wrap the mesh around the base and the back twice. Secure with twine
Cover the hay base with pieces of sod cut with a utility knife to fit around the hay.
Wrap the covered sofa with the burlap lightly until the vertical pieces of sod are attached to the hay.
Water regularly to encourage the sod to take hold on the hay. Burlap mesh can be removed when the sod is firmly rooted to the hay.