To custom design a 304 stainless steel cabinet, you will need to work with a manufacturer or fabricator who has experience working with this material. Here are some steps you can follow to get started:

　　Determine your needs: Think about what you will be using the cabinet for and what features you need it to have. Consider factors such as size, layout, and storage capacity.

　　Sketch out a design: Create a rough sketch or drawing of the cabinet layout and dimensions. This will help you visualize the finished product and communicate your ideas to the manufacturer.

　　Choose a manufacturer: Research different manufacturers or fabricators who specialize in 304 stainless steel cabinets. Look for companies with a good reputations and experience in creating custom designs.

　　Work with the manufacturer to finalize the design: Share your sketch and ideas with the manufacturer and work with them to finalize the design. They will be able to provide input and suggestions based on their expertise and experience.

　　Place the order: Once the design has been finalized, place an order with the manufacturer. They will provide you with an estimated lead time and cost for the project.

　　Install the cabinet: Once the cabinet has been manufactured and shipped to you, you will need to install it according to the manufacturer's instructions. If you are not comfortable with this process, you may want to hire a professional to do the installation for you.