Remove the slipcover from the chair and rip open the seams with a pointed scissors or seam ripper. Separate the front piece from the curved piece.
Trace the shape of the arm cover pieces on paper to make a pattern. Cut the two pieces out of a coordinating upholstery fabric for each arm slipcover you are making.
Pin the rounded edge of the front slipcover pieces to the front edge of the arm cover piece so the right sides of the fabric are touching. Refer to the original slipcover pieces to see how the pieces fit together.
Sew the two pieces of the arm slipcover together with a 1/4-inch seam.
Fold the raw edges of the slipcover 1/4 inch to the wrong side of the slipcover, and then fold it another 1/4 inch to make a clean edge. Pin the folded hem to hold it while sewing. Secure the hem by sewing the edge with a straight stitch.
Repeat the cutting and sewing steps for each arm slipcover.
Spray the right side of the slipcover with a stain-protecting upholstery spray to help keep the slipcovers clean.