A separate work area about 5 feet wide located at one end of a side bench is a great convenience. This can be just a piece of 1/4- or 1/2-inch Masonite placed on top of an empty bench space, or a more elaborate potting tray consisting of a flat work space with sides and back of 12-inch lumber about 6 to 8 inches high. Here you can pot plants or bulbs, sow seeds and transplant seedlings, even keep records.
However, if you cannot spare permanent room for these doings, you can let a wide board serve as a portable area. Select a board long enough to reach across the walk from bench to bench. When not in use, it can be placed out of the way under the bench.
Supplies of sand, soil, peat moss, perhaps fir bark, need to be at hand. Bins that can be tilted forward for easy access are fine, built in under the work area, but plastic or metal containers with lids or step-on openers are quite adequate and colorful, too. You can use wooden boxes or nail kegs, or perhaps improvise something from materials at hand. My first "storage bin" was a small old round-topped trunk from the attic which fitted in nicely at the end of the center bench.
The sizes of storage containers depend upon your operations. If you are growing mainly bench plants, you will need extra soil only for an occasional pot plant or bulb-pan, once the benches are filled, and storage containers can be small. However, where you grow mostly pot plants, large storage containers are necessary if adequate supplies are to be available, particularly in winter when bad weather may prevent your obtaining additional materials for late-season transplanting or preparation of flats for early sowing.