Check all corners of the artwork to be matted, to ensure they make 90-degree angles. Trim the artwork as needed, using a paper cutter.
Measure the acid-free, lignin-free poster board. Use a carpenter's square to make sure all corners are 90-degree angles. Cut the poster board to the desired length and width of your mat, two inches larger all around
Apply a light coating of acid-free, lignin-free adhesive to the poster board mat, and to the back of the artwork. Press your artwork onto the mat, smoothing it from the center to the top, from the center to the bottom, from the center to the left, and from the center to the right, to remove any air bubbles. Allow the adhesive to dry.
Hang your artwork to its best advantage. Remember to protect your artwork from direct sunlight.
Frame art after matting. This will increase its value and protect the art from dust and light damage.