If you have a Tractor Suppy Company near you,they use thick blocks of styrafoam to protect some of their equitment they get sent to them.
All you have to to is ask and they will give you as many as you want for free.Most of them are the same size..About 18" long,10"wide and 8"thick.
Your arrowswill pull out very easy also.They also last along time.I use them with target points and broadheads.
You can also use a cardboard box.Stuff as many plastic shopping bags in the box as you can.I hope this helps.