<b>Arms</b> Pin some oversized fabric to the outside and inside of the arms, wrong side up. Make sure the fabric is properly tensioned across all faces, but is not too tight, and mark the curve or line of the arm with chalk. Remove from the chair and perfect the line. Add a seam allowance and cut.
Cut these pieces as a template for the opposite arm, remembering that the fabric needs to be the opposite way. Now bring all the pieces back to the chair and pin in place, wrong side up.
Measure the arm borders, add a seam allowance, and cut the fabric. Bring the border to the chair and pin in place. Line up the edge of the border with the edge of the inside and outside arms. Pin together. When everything is in place, notch the fabric in a few places just to be extra safe. Remove from the chair.
Machine-stitch the arms together so that the tension between the inside arm and seat is correct and not over pulled. Bring back to the chair.
<b>Back and Seat</b> Measure and cut (with seam allowance) your inside back and seat. Place the fabric wrong side facing out on the chair and pin to the bottom of the inside arm and the side of the seat, one from the seat top to the bottom of the chair, and one from the front of the seat to the back. You'll need to make a few small release cuts to help ease the fabric round the curve of the front of the seat. Bringing these seams together can be fiddly; it might help to sew one seam, bring the cover back to the chair, then mark and sew the next. Remember that the finished seam on the front will be very visible, so make sure it is straight.
Measure and cut the fabric for the outside back with a seam allowance. Place the labrics wrong side up and pin to the inside back and outside arms. If your chair is bigger at the top than it is at the bottom, it's likely you'll need to add a zipper on one side of the back.
Turn up the hem along the bottom of the chair and pin. Make the drop just a touch longer than the chair itself. Remove from the chair and machine together. If you don't want any visible stitching, use some fusible tape and iron together instead.
<b>Tips</b> The slipcover should not be too tight in the areas where the back and the arms meet the seat. There needs to be just that little bit extra that can be tucked in to prevent the seams from ripping when you sit in the chair. If your chair is an awkward shape, just lay some oversized fabric in place and pin. Remove from the chair, measure the seam allowance, and cut.
Excerpted with permission from <a href="http://www.amazon.com/gp/product/0762447680/ref=as_li_qf_sp_asin_il_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0762447680&linkCode=as2&tag=craftfocom-20">"Style, Stitch, Staple: Basic Upholstering Skills to Tackle Any Project"</a> by Hannah Stanton and published by Running Press.