Step 1: What You Need. Measuring, Cutting , Glueing and Taping .
hot glue or a strong glue
stamped /plain fabric or plastic ( in my case a leppard stamped plastic )
foam ( optional ) if you want it more comfortable
hot glue gum
scissor and/or utility knife
There are quite a few pictures in the next steps , and they are self-explanatory.
1) Measure and cut the cardboard at your size choice.
2) After make an "X" put it inside a cylinder folded cardboard . Apply hot glue and tape.
3) The last picture shows the final result, i filled the gaps with more cardboard to make it stronger .