Place your first piece of prewashed fabric face down up the back of the chair from the floor, over the top and down to the chair seat. Cut the fabric at the chair seat with a 1/2-inch seam allowance and a 1/2-inch hem allowance. If you are using patterns, florals or stripes, be sure to match your designs so that the fabric pattern goes the same direction on the furniture.
Pin along the sides of the chair straight down from the widest part of the chair back. Leave a 1/2-inch seam allowance. Cut a piece of fabric that overhangs the top of the seat 1/2 inch on all sides. Pin the back edge along the bottom of the seat back.
Measure the width of the sides from the back leg, across the front legs and along the other side to the back leg. Add 1 inch for seams. Measure the height from the top of the seat to the floor and add 1 1/2 inches for seams and hem. Allow a little extra fabric for variation in the hem length. Cut the fabric. Pin the fabric to the rest of the slipcover at the seams. All the fabric pieces should be pinned face sides together.
Sew the slipcover together using 1/2-inch seam allowances. Clip the corners and ease your seams. When fabric is sewn to fit a corner it will bunch up in the pointed part of the corner. To reduce this excess, it is common to clip the corner seam allowance fabric close to the seam at the corner. To ease a seam means to cut small V-shaped wedges in seam allowances that are going around corners. This will allow the fabric at the seam to bend more easily.
Turn the cover right side out and fit it over the chair. Make any adjustments you need for the best fit. Pin up the hem once you are certain the cover is finished. Hem with the sewing machine.