Here is a quick and simple mobile stand made from a single A4 paper(you will need a stapler too) in 5 mins
Step1: Start with an A4 size paper
Step2: Fold half-way along length
Step3: Repeat again to reduce to quarter width by folding along the length
step4: Fold to make a triangle at one end
Step5: Fold to make a smaller triangle at other end
Step6: This is how the folded paper should look like at the end.
Step7: Staple as shown in the picture
Some picture of the stand holding the phone.