Screw together many long pieces of pallet together with supports under the length of them. screw in 4 legs to the underside of the top of the table.
Instructable on how to build a pallet table and pallet chair.
Step 1: The Chair
Cut boards to the size you want and screw them together with longer pieces underneath to create the base of your chair.Then cut two long pieces and screw them together with shorter pieces of wood. to make the upper rest. Do the same with even longer pieces for the main back of the chair.