What could be more simple for turning a paper plate in to a craft than making a round object like the earth. All you need is a paper plate, blue paint, paint brush, green tissue paper and glue*. No need for scissors so this is an easy craft for even the littlest ones to do.
Have the child paint the outside of the paper plate blue. You or the child can tear off pieces of green tissue paper. Let them glue it to the plate in a way they think the Earth looks.
*If you have your "land" pieces torn out already, you can press them in to the wet paint and they will adhere and you will not need any glue.