First, pack them one inside another and under beds is an ideal place to store them.
I like to pack mine together and then if there is still more space, fill them up with things that I only use occasionally like seasonal decorations or packing material that I don't need very often.
Hi ! Keep out of season clothes in them , that will free up more closet or dresser space , keep them under your bed or in an attic .
I would also fill with items not used very often but if you can stack them they can be used for an end table, etc. To steady you can use bungee cords. I have one as a bedside table and placed it on an old iron TV stand that I painted, connected with the bungee cord then covered that area with a pretty doily. Works great! Good luck!