For a finished look, add recycled plastic shutters to the sides. Use decking screws to attach the shutters. Paint top edge of wood sides to match shutters.
Staple landscape fabric to the inside of the pallet box. Add a layer of small drainage stones on top of the fabric.
Cut another piece of landscape fabric and lay it over the stones. Add one more layer of stones, then top with compost and soil mixture.
Lay out flowers and vegetables according to space instructions on their containers. Plant and water.