I want a phone cover cheaply so an Idea came to my mind to do it with a balloon
Step 2: Making the Cover
1.Blow in the balloon(as shown in figure 1)according to your phone size.
2.Put your phone on the balloon,as shown in figure 2 .
3.While pressing your phone on balloon remove the air in the balloon slowly by opening its nozzle of the balloon.As shown in figure 3.