Look on the back of the cushions for a zipper. Unzip the slip cover and remove it from the cushion. Turn the slip cover inside out and use a seam ripper to gently remove the seams. When the pieces are completely disassembled, you'll have a pattern for your new slip covers.
Lay the fabric out with right sides together. Place the pattern pieces on the fabric, ensuring that florals and stripes run the right way. Pin the pattern pieces in place. Cut the fabric out, using the patterns as a guide. Remove the patterns from the slip cover pieces.
Sew the slip cover pieces, placing right sides together. Reuse the zipper that came from the original cushion if it is in good condition; otherwise, buy a new one. Install it by fitting it into the panel on the back part of the slip cover. Use a zipper pedal to sew it in snugly into place.
Clip the corners of the slip covers with scissors so they lie flat. Iron the seams open. Turn the slip covers right side out. Slide the cushions into the slip covers and zip the covers shut. Replace the cushions on the couch.