Use white glue or tape to stick the sides shut. Leave one edge open.
Insert a small, battery powered LED light through the open edge.
Pro tips!
To make your lantern more sturdy and water resistant, use clear packing tape to cover both sides of the paper after cutting out the parts. Overlapping the edges of the tape slightly keeps the surface sealed completely. Working on a non-stick surface, like parchment paper or a silicone baking sheet, makes this step easier.
The paper tabs will leave a dark shadow once the light is placed inside. This can be minimized by replacing them with tabs made of clear packing tape. Attached a piece of packing tape where the tabs were; fold in half with the sticky side in; trim the excess and proceed as above.
