Measure the body of the reclining couch, from one arm to the other for the length and from the floor in front and over the seat to the floor in back for the width. Add 12 inches to the measurements and write down the exact and adjusted numbers on a piece of paper.
Measure the length of the couch arm, from the front-most point to the rear edge and increase the number by 12 inches. Measure arm width of the recliner couch, from the side floor and over the top of the arm to the seat. Add 2 inches to the width measurement. Write down both the exact and adjusted numbers of the measurements.
Cut three pieces of fabric to construct the slipcover. Use the measurements in Step 1 for the main body piece and the measurements in Step 2 for the two arm pieces.
Lay the main body piece of fabric over the seat and back of the couch, so the bottom edges touch the floor. Tuck excess fabric into the seat cushions. Lay the arm pieces over the armrests and pin the edge that meets the body piece together so the right sides are touching.
Remove the fabric from the recliner sofa and sew the arms to the body using a half-inch seam. Lay the fabric back on the recliner, tuck the excess fabric into the cushions and verify the arms are in the correct location. Adjust the seams, if needed.
Cut the front edge of the fabric vertically on both sides of the recliner footrest, from the floor to the seat cushion. This lets you raise the footrest without pulling on the slipcover.
Pin the side edges on the front and rear corners of the slipcover so the right sides are touching. Remove the slipcover from the recliner couch and secure the edges with a half-inch seam.
Hem the bottom edge and the footrest slits by turning the edge a quarter-inch from the back side of the fabric, and then another quarter-inch. Pin the hem to hold it in place, and then sew it close to the first fold to secure.