I made these clay treasure chests with grade 2, but this would work with older children too.
Boxes were made with slab construction by creating a bottom, two side pieces and two end pieces and joining together with a lot of slip and extra clay! Boxes were decorated with padlocks, handles and rivets and clay tools were used to scratch in a wood grain texture. Later we also created a lid piece and after firing, chests were painted in brown and metallic paints.
They came out a bit rough looking - but I think it makes them look quite rustic and authentic.
For display I filled the chests with sequins to look like shiny treasure!