The C shape that grips onto the table is set, but I left the hook very simple. You can customize this part to be whatever shape best suits your needs.
Use either double sided tape or small tabs to secure the hooks in place. Mill the design out of your choice of MDF or experiment with new materials.
Use this EASEL link
Use either super glue or wood glue to adhere the parts together. Use small dots to avoid overflow. You can stack as many as needed. 4 parts wide works well for backpacks and bags, a 2 stack is great for keys