Glue the two crates together at the end. Allow glue to dry.
Make four pilot holes with drill where glued and then screw together.
Measure the inside of the bottom of the crates. Cut to length. Glue the two strips of wood inside the crate along the outer ends. Allow to dry and then screw to secure.
Glue the French rolling pin to the inside of crates at all four corners. Allow to dry.
Make a pilot hole. Screw the legs in from the top of bench in between slats in through the scrap wood into the top of leg.
Make a pilot hole. Countersink holes with 3/8" drill bit and screw legs in from the outside into the leg. Fill in holes with wood filler.