Miter cut the trim to fit around the edge of the plywood. Measure inside to inside to get an accurate cut. Glue and nail the trim into place and into the legs to help stabilize them. Recess the nails using the nail punch.
Paint or seal the legs and base (if old paint, follow lead rules). Fill nail holes with wood filler and paint over.
Stand the base up and place suitcase on top (Image 1). Open the lid and screw the suitcase to the base using screws that will not punch through the width of the wood underneath (Image 2).
Joanne Palmisano is the author of Salvage Secrets (W.W. Norton, September 2011). Visit her blog, also called Salvage Secrets.