Aspenite is not very robust and considering it's only 5mm thick you know this wouldn't make stable shelves easily.
So I built triangle support. I'll show you in this instructable.
Step 1: Back Board
So I came up with a board like shown on the picture.
(Note: it's possible to first create the board and cut the droves, but it's better actually to first build the shelves and then dig the droves accordingly to where their burrs come.)