The climate in Britannia was humid and wet most of the year making solar evaporation impractical. Clay deposits however were plentiful and common. The materials along with fuel for the fires were readily available year round and pottery could be fired in the rainy season allowing the workers to focus on salt production in the relatively drier summer months. Though making salt using briquetage was labor intensive the rough clay pottery used the labor was cheap and required relatively low skills, important factors as they had to produce vessels and supports in large volume to repace what was broken in the process.
While much of the salt in the roman diet was already in their food when they bought it at market, markets were not always available in the the ever expanding empire. Roman soldiers required salt to replace vital electrolytes and to preserve food as they expanded the Empire. Salt was a part of thier standard supplies and new salterns were built as often as possible to keep costs low and continue suppling the military as well as the common citizens. Salt was heavy and difficult to transport far even along roman roads. Traveling with loose salt was prone to hazards such as moisture damage and spillage, so condensing the salt into cakes would have made it more portable for trade and travel .