1.Cut 2 pieces of fabric, each measuring 52 cm x 52 cm, for the top and bottom of the cover (1 cm seam allowance included). Cut 4 pieces of fabric, each measuring 52 cm x 12 cm, for the sides of the cover (1 cm seam allowance included). Sew the 4 sides together at the short ends to make a ring. Start and stop 1 cm from the edge. See fig. 1. Press the seams apart. 
2.Sew the first zip onto one of the sides. Start at the corner and stop 5 cm before the next corner (the zip is approx. 5 cm too long). Sew the other zip. Start at the same corner and stop 5 cm before the next corner. The two zip sliders should meet at the same corner. See fig. 2. 
3.Sew the first zip onto the base piece. Start at the corner and stop 6 cm from the edge. Sew the other zip. Start in the same corner, stopping 6 cm from the edge. See fig. 3. 
4.Close each zip by approx. 7 cm. Sew across the zips 4 cm from the end. Cut the excess 3 cm of zip off. Sew the rest of the seams on the base and sides together from zip end to zip end. See fig. 4. Press the seams. 
5.Sew the top onto the sides. See fig. 5. Press the seams. 
6.Turn right side out and insert the cushion into the cover. See fig. 6.
