Diy Seedling Rack . There are two big components to the plumbing: They can be linked together or flush mounted depending on how you configure your growing system. 1/2/4pcs Wall Mounted Hanging Wooden Rack Storage Shelf DIY Plant from www.aliexpress.com Seed starting pots ~ our preference is 5” square pots. 4 trays will fit on each shelf. It can grow over 800 seedlings if 72 pack cell inserts are used.