1. Making sure your crates are sanded, line up two crates next to each other longways, and use wood glue to glue them together. Use clamps to hold the crates in place while drying, and then follow with screws.
2. Use the measurement of the length of the crates together and the depth of of one crate for your top and bottom pieces of wood.
3. Attach legs or casters to your bottom piece using screws.
4. Pre-drill 2 holes in the center of each side, and follow up with screws into the bottom of your connected crates.
5. For the upholstered top, lay a sheet of fabric, batting, foam board, and wood. Start by attaching the foam board to the wood with an adhesive spray. Having the foam board touch the batting. Pull batting tight around the 2 pieces and use staple gun to attach it to the wood. Cut off excess once attached.
6. Follow up with the fabric. Repeat the process making sure to tightly wrap fabric around all sides and corners. Cut off excess.
7. Attach the upholstered top with wood glue and use clamps to hold in place. Follow up with several screws going from both crates into the upholstered top.
8. Optional: add cabinets or shelving to crates. Stain bench.