Where picking time goes
In a manual picking operation, a large share of a picker’s time is usually spent moving rather than picking. Walking between locations, reaching for high shelves, and waiting for access in a crowded aisle all add up. Improving layout and slotting targets this directly: it makes the necessary trips shorter without asking anyone to work faster.
Layout is the physical arrangement of the space: aisles, racking, packing and staging areas. Slotting is the decision about which product goes in which location. The two work together. A good layout with poor slotting still wastes steps, and clever slotting in a poor layout hits limits.
Start with how the flow runs
A sensible layout follows the order’s journey: stock comes in at receiving, is stored, is picked, and finishes at packing and the dispatch area. Where possible, the flow should move in one general direction, so that people and goods do not cross paths repeatedly.
Useful principles include:
- Place packing close to the most-used picking locations. Items that travel the shortest distance to the pack bench save the most steps.
- Keep aisles wide enough for carts or the equipment used, and keep them clear.
- Separate receiving from dispatch if space allows, to avoid congestion at busy times.
- Leave room to grow. A layout that is full on day one forces rushed changes later.
For a very small home setup the same ideas apply on a small scale, as covered in the guide to home-based shipping.
Slotting by velocity
The central idea of slotting is that the products picked most often should be easiest to reach. To do this, rank products by how often they appear in orders. This is the picking frequency, sometimes called velocity.
A common approach is to sort products into three rough groups:
- Fast movers, the small number of products that account for a large share of order lines.
- Medium movers.
- Slow movers, the long tail picked only occasionally.
Fast movers go in the most convenient locations: near the pack area and between waist and shoulder height, where picking needs no bending or stretching. Slow movers go further away or on higher or lower shelves. Order data usually shows a heavily uneven pattern, with a minority of items driving most picks, though the exact split varies by business, so check your own history instead of assuming a figure.
Count order lines, not units sold. A product sold in large quantities but in a few orders is picked less often than a cheap item that appears in many orders. Picker walking depends on the number of visits.
Other slotting factors
Velocity is not the only rule. Several other considerations modify it.
Size and weight. Heavy and bulky items belong low and near the exit, both for safety and to avoid carrying them far. Light, small items can use upper shelves and small bins.
Fragility and hazards. Fragile items should not sit beneath heavy ones. Products that require special handling, such as liquids or batteries, may need separate storage and are subject to rules around dangerous goods.
Affinity. Products frequently ordered together can be stored near each other, so a single trip collects both. Analysing past orders shows which pairs recur.
Similar-looking items. Putting near-identical products side by side invites wrong-item picks. Separating them, or using clear location labels, reduces mistakes, which is the same issue that verification at the pack station aims to catch.
Variants. Sizes or colours of the same product are often kept together for tidiness, but if one size is far faster than the others, it may deserve a better spot.
Seasonality. Items that spike at certain times may move forward before the peak and back afterwards.
Location labelling
Slotting only works if people can find the slot. Use a consistent location code, for instance aisle, shelf and position, printed clearly at the location. Keep the system’s record in step with the shelf: if an item is moved, update the record the same day. A location that is wrong on paper but right on the shelf (or the reverse) generates searches and errors, and the stock record becomes unreliable. A warehouse management system helps by directing pickers to locations and enforcing updates.
Reslotting without chaos
Demand changes, so slotting needs review. But moving stock takes labor and can temporarily slow work, so do it deliberately:
- Review picking frequency periodically, for example quarterly, or ahead of a known peak.
- Identify the few moves with the largest benefit, such as bringing a new best seller closer or sending a faded product to the back.
- Schedule moves for quiet periods.
- Update records and labels at the time of the move.
- Tell the team, so nobody walks to the old location.
Small, regular adjustments tend to be safer than occasional total reorganisations.
How to tell if it worked
Measure picks per hour or the average time to complete an order before and after a change, over comparable periods. Watch error rates too. Reducing walking should help, but if errors rise because items have been moved without clear labelling, the gain is false. Layout interacts with picking methods, so a change to batch or zone picking may call for a fresh look at slotting.
Remember that returns and incoming stock also need a home. If space for them is not planned, they end up in aisles and undo the improvement.