Cut the poster board or card stock piece into a 12-by-12-inch square. You can also make a smaller cone with a little 6-, 8- or 10-inch square.
Set the square on a flat work surface with one point or corner pointing downward. Set the point of a compass on the bottom point of the paper square. Drag the pencil point of the compass across the paper center creating an arc from the right corner to the left corner.
Cut along the pencil line with scissors or a craft knife.
Hold one side of the arced area of the shape with your fingers placed at the center. Roll one side of the card stock toward the other side while forming a cone shape. Make sure that the bottom is tightly rolled shut.
Place the stapler inside of the top of the cone and staple the top sides of the card stock or poster board in place to keep the cone from unraveling. Staple the cone interior as far down into the hollow as the stapler will reach two or three more times. This is the back of the cone.
Cut a 10-inch piece of ribbon or lace. Form the material into a loop and staple it into the back of the cone for a hanger. Place the bouquet of flowers into the cone.