Cushion mattress

I have the material and the cushions, now to make a mattress inspired by this. 

My mum had lots of cushion inners from her work that were going in the rubbish so I grabbed some. I had seen this on a friends Pinterest board with the idea to sew together 5 pillowcases and insert pillows and, voila, instant mattress. I figured it would be cheaper to buy 1 big piece of material and sew divisions and add velcro. The material is drill as I think this will be used on our deck this summer, so wanted it to be reasonably hard wearing.

I'll update with more photos as I get it made. Actually, should go and sew some now.