A simple-to-understand corner upholstery technique is to fold the corners gift-wrap style, as if you are wrapping a package. While you may have your own take on wrapping packages, the basic method is to tuck under the corner flaps gently at approximately a 45-degree angle so the entire flap of material looks symmetrical with two angled corners. Fold the flap down and staple it several times to secure it to the project. Repeat the folding and flap-making process on the other side of the project, stapling it in the same fashion. here