By the way...! You can use a pallet mattress as a floor cushion or dog bed.
1.Cut mattress cover pieces (all dimensions include 1 cm seam allowance): 2 pieces, each 122 x 82 cm for the top and base, 2 pieces, each 122 x 12 cm for the long sides, 2 pieces, each 82 x 12 cm for the short sides 
2.Sew all 4 side pieces together to form a ring. Start and end 1 cm from the edge. See fig. 1. Press the seams flat. 
3.Mark the centre point on one long side and the centre point on the long side of the base. Sew zipper onto one long side. Start at the mark and end 5 cm from the corner (the zipper is about 5 cm too long). Sew the second zipper so that the two zipper sliders meet at the centre. See fig. 2. 
4.Sew the zippers onto the base. Start at the mark and end 6 cm from the edge. See fig. 3. Sew the last centimetres (i.e. from the corner to the zipper). 
5.Sew the other 3 sides of the base. Sew the top onto the sides. See fig. 4. Press the seams. 
6.Turn your mattress cover to the right side. Insert the foam mattress. See fig. 5.
