Measure the chair with a tape measure. Take measurements of all removable cushions, back, arms, front, seat and sides. Add 1 inch to each measurement for the seam allowance.
Transfer the measurements to brown paper to make a pattern. Cut out all pattern pieces and fit them to the chair using upholstery pins to hold the pattern in place. Make any adjustments as necessary.
Purchase fabric. Lay out fabric on a flat surface, right side up. Trace pattern onto fabric. Cut out fabric with scissors.
Pin each section of the cut fabric and test the fit on the RV chair prior to sewing. Make any adjustments. If using decorative piping, add it between the fabric pieces. Pin seams and sew, starting with the largest pieces first and ending with the removable cushions.
Add hook and loop tape to the back of removable cushion pieces. This will hold the cover secure while allowing for easy removal when the slip cover needs to be cleaned.
Snip all loose threads with scissors. Trim seams with pinking shears for a professional finish. Press seams open. Zigzag stitch seam edges to secure. Place slip cover on chair.