You will need scissors, ruler, cardboard box, brown paint, small mirror, paintbrush, plasticine, shells, plus bits from the garden such as gravel, moss and twigs.

If the box is deep cut the side so that it is about 4 cm or 2 inches in depth.  Paint it brown and allow the box to dry.  Place the mirror in the box to form a pond.  Place moss, shells, cones, twigs etc in the box using the plasticine to stick the twigs into.  Scatter some gravel in the box.

Here are some more craft ideas for kids:
Growing a Pineapple
Painted Terracotta Flowerpots